On fatigue life under stationary Gaussian random loads

Ramesh Talreja
1973 Engineering Fracture Mechanics  
97201.--The maturation of the cochlea is often emphasized when correlating physiological, behavioral, and anatomical data with hearing inception, but the contribution of the conductive mechanism must also be considered. This study compares the development of all parts of the ear in the rat from 11 days postconception to 1 month postpartum. Although the hair cells are distinguishable at birth, the remainder of the organ of Corti is poorly differentiated. The external auditory meatus is closed,
more » ... e middle ear is filled with a gelatinous mass, the ossicles are cartilagenous, and the stapes is continuous with the otic capsule. Maturation of the cochlea is seen first in the basal coil at eight days postpartum, evidenced by the appearance of the tunnel of Corti, the extracellular spaces between the hair cells, and nerve fibers crossing the tunnel. At this time, however, the external meatus is still closed, some gelatinous material is still retained in the middle ear. The stapedio-vestibular "ligament" is composed of cells rather than fibers, limiting its flexibility. Structural differentiation of the cochlea proceeds from base to apex, being completed by the 17th day. The annular ligament does not lose its cellular component until the 21s day. A2. Auditory Sensitivity in the Tadpole (Rana catesbeiana). a. , New Jersey 08540.--Auditory sensitivity in six bullfrog tadpoles was investigated by electrophysiological techniques. Tonal stimulus intensities that generated a standard potential of 0.1 ttV in the inner ear showed a hearing range from 100 to 4000 Hz with maximum sensitivity near I dyn/cm: (0.1 N/m:) in the lower portion of the range. The data also indicated that tadpoles lack the place mechanism of adult frogs and thus place as a mechanism appeared at the amphibian metamorphosis in the course of the evolution of vertebrate hearing. A conditioned suppression technique has been applied to five agoutis and behavioral thresholds measured. Each animal was water deprived and allowed to drink only in the experimental situation. Training was effected by pairing audible tone pulses with shock until the subject learned to cease drinking reliably in the presence of a signal. Auditory thresholds were then assessed at octave intervals. Maximum sensitivity occurred at 8 kHz (0 dB re 2X10 -4 dyn/cm•), a high frequency cutoff at 64 kHz, and a low-frequency cutoff at 500 Hz. Low-frequency sensitivity may have been impaired by masking or TTS resulting from the loud licking noises produced by this species, although control studies have not verified this hypothesis. It is the authors' opinion that hearing in the Agouti is oriented toward the higher frequencies despite the presence of certain low-frequency structures such as the large bulls. The observed high-frequency bias supports previous findings regarding this animal's basilar membrane. A4. Sound laressure Transformation from the Free Field to the Eardrum. E. A. G. Sanw, Division of Physics, National Council of Canada, Ottawa, K1A OS1, Canada.--The sound pressure transformation by the human head and external ear has been the subject of many measurements over a long period of time. The average acoustic properties of the external ear are now established sufficiently well that diverse data can be brought into a common set of reference frames. Data from 10 studies in five countries are presented in terms of eardrum response at eight azimuthal angles as functions of frequency from 0.2 to 12 kHz. Data from the same pool are also presented in terms of azimuthal variations and interaural level differences at 18 frequencies. Where there is lack of agreement between studies, the presentation often indicates the probable causes. A critical examination of all the data leads to self-consistent families of average response at the eardrum position as a function of frequency and angle of incidence in the azimuthal plane. An extension of the method should provide useful estimates of average response at angles of incidence not on the horizontal plane. A5. Aural Noise as a Function of the Cardiac Cycle. D. R. Soo•ilQuisx, J. W. LiNr•sEv, AND M. R. HAIlTEa, Department of P•ychology, University of North Carolina at Greensboro, Greensboro, North Carolina 27412.--lnvestigators have suggested several internal noises that affect absolute thresholds (e.g., heart sounds, circulatory pulsations, muscle tremors). Furthermore, it has been suggested that blood flow may The Journal of the Acoustical Society of America 291 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA modulate aural noise in the external canal. Since mental blood vessels cannot expand outward due to bone encasing the canal, an inward expansion is suggested which induces an increase in aural noise by decreasing mental volume under the earphone. In short, the mental pulsation hypothesis (MPH) suggests a modulation of aural noise as a function of blood flow through the ear canal. This study examines the MPH under three conditions (tight and normal fitting supraaural cushions and an insert earmold) as a function of the cardiac cycle. Three dependent measures were obtained, viz., EKG, blood flow at the earlobe, and presstire changes within the ear canal (positive pressure indicating, according to the MPH, an inward expansion of the blood vessels). The EKG R-wave keyed a signal averaging computer which in turn averaged the data over 32 separate heartbeats. Results indicate: (1) a maximum positive pressure approximately 225-250 msec after the R-wave with rapid decreases prior to and immediately after the maximum (tight fitting earphones); (2) no systematic pressure change with normally fitting earphones; (3) an inverse relationship between blood flow at the earlobe and pressure change within the meatus. The maximum negative pressure occurring near 225-250 msec after the R-wave. A6. Morphological Correlates of Asymptotic Temporary Threshold Shift in Chinchillas. DAWD L[M AND WILLI*•I M•LNIC•t, Department of Otolaryngology, The Ohio State University, Columbus, Ohio 43210.--Using the scanning and transmission electron microscopes, an attempt was made to cor- relate morphological and behavioral data from conditioned chinchillas following their exposure to a presumably subtraumatic level of noise that produced asymptotic TTS. Varying degrees of morphological change in the sensory cells, which could be attributed to the noise exposures, were observed in these animals. Changes included giant cilia formation, sensory cell debris, cellular swelling, and scar formation. Changes also appeared in the stria vascularis. These morphological changes were most pronounced in the apical turn of the cochlea. Our preliminary data appear to support the idea that sensory cell degeneration occurs even after exposure to a noise level considered subtraumatic and which apparently does not produce permanent changes in behavioral threshold hearing levels. A7. Anatomical Correlates of a Temporary Shift in the Threshold of Hearing. B. A. BOHNE, Department of Otolaryngology, Washington University and Central Institute for the Deaf, St. Louis, Missouri 63110.--When chinchillas are continuously exposed for more than 24 h to an octave band of noise centered at 500 Hz, the behavioral TTS for 715-Hz tone stabilizes at an asymptotic value proportional to band level [Carder and Miller, Trans. Amer. Acad. Ophthal. Otolaryng. 75, 1346 (1971) ]. Recovery to normal thresholds requires from two to seven days. Chinchillas were exposed to this same noise for two days at 65, 75, 85, or 95 dB SPL. The organ of Corti was immediately fixed and prepared as a flat, whole-mount specimen in plastic suitable for both phase contrast and electron microscopy. Other ears exposed at 95 dB SPL were allowed to recover 7, 28, or 70 days before fixation. The number of cisternae in the peripheral membrane system of many outer hair cells was increased from three to six to as many as 30. Similar membranes appeared as whorls within the cells. The proportion of altered cells was greatest in upper second and lower third turns and increased with exposure levels. Recovery toward normal membrane configuration was evident at seven days and only minor variations remained after 28 and 70 days. AS. Guided Interfacial Waves with Applications to Cochlear Mechanics. R. J. CLIFTON, Professor of Engineering, Brown University, Providence, Rhode Island.--Waves are considered which propagate along a membrane separating two compressible, inviseid fluids. Capillary forces and membrane tension are assumed to provide the stiffness for the membrane. Dispersion relations are derived for cases of (i) an unbounded region, (ii) a channel for which the particle velocity at the sides is perpendicular to the interface, and (iii) a slit for which the particle velocity at the sides is parallel to the interface. The solution for the latter case is obtained by first solving the problem of diffraction of interfacial waves by a rigid plate in the plane of the interface. Results of case (iii) are used to examine the importance of interfacial waves for wave propagation in the cochlea. Preliminary evidence indicates that such waves may be of primary importance for frequencies in the upper part of the audible range. A9. Measurements of the Transient Response of the Basilar Membrane Using the Miissbauer Technique. L. ROaLES, W. consin 53706.--Measurements were performed on 25 sqnirrel monkeys, using an experimental preparation identical to the one nsed by Rhode to measure frequency response [J. Acoust. Soc. Amer. 49, 1218-1231 (1971)]. The stimuli used were acoustic clicks, about 150t•sec in duration, presented in sequences of 100 000 to 400 000. Clicks with differcut amplitudes were used, and the responses of the basilar membrane at a point in the basal turn and of the umbo were measured. The results indicate that the click response of the basilar membrane at the points measured is a lightly damped oscillation with a natural frequency between 6 and 8 kHz. There is an initial part of the response that has a faster decay and a later part that has an extremely slow rate of decay. This later part of the response displays a nonlinear behavior for changes in amplitude of the stimulus. Even when the general features of the vibratory pattern were stable for a period of hours, there was usually a marked decrease with time in the number of cycles which could be observed. [Supported by N 1H Grants.] AI0. Eardum Displacement Following Stapedius Muscle Contraction. A. YoNovi•z AN• J. D. HAm•IS, U.S. Naval Submarine Medical Center, Submarine Base New London, Groton, Connecticut O6340.--Simultaneous monitoring in human subjects on the same ear of eardrum displacement by tympanomanometry, and acoustical impedance by the Madsen bridge, provided information concerning contraction of the stapedius muscle and its effect on eardrum displacement. Extensive control procedures were employed to elicit only the stapcallus: lower-intensity auditory stimulation, electrocutaneous stimulation of the homolateral external ear canal, and anesthetization of nerves leading to the tensor tympani. (1) Extremely small biphasic and monophasic eardrum movements were seen in the stapedious-only ear to auditory and electrocutaneous stimulation; the form of the response was much less predictable to auditory stimulation. (2) At higher sound intensities, relatively large inward and biphasic movements of the eardrum occurred in the normal ear, unquestionably resulting from contraction of the tensor tympanJ. These results were further validated in a group of stapedetomized ears, without the stapedius but with normal tensor tympani. O) Biphasic responses did not occur in the tensor 292 Volume 53 Number ! 1973 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA tympani-only ear only monophasic inward responses. (4) Upon air-jet stimulation to the orbit of the eye, these subjects had an accentuated tensor response in that large inward movements of the eardrum occurred as compared to those in normal ears, suggesting that there is an alteration of the tensor response by the presence of the stapedius muscle. Estimates of the actual eardrum displacements were calculated based on a model of the external ear canal and eardrum. A11. Abstract withdrawn. AI2, Tympanic Muscle Effects on Middle-Ear Transfer Characteristic. ALv•Eo L. NUTTiLL, Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan 48104.--The change in the magnitude and phase of sound transmission through the guinea-pig open-bulls middle ear is measured when two levels of independent, isotonic, tympanic muscle contraction are effected by direct electric stimulation of the muscle bodies. Both middle-ear muscles attenuate the passage of low-frequency vibration giving the largest attenuation for frequencies below 300 Hz, the tensor tympani producing 28 dB maximum attenuation, the stapedius producing 10 dB. In the 1-to 3-kHz frequency range, both muscles are capable of generating an apparent gain in transmission: the tensor tympani giving a gain of 5 dB at 2.5 kHz for maximum contraction, the stapcallus 0.5 kHz at 2.5 kHz for maximum contraction. The phase shifts for all contraction cases were leading phase functions. Changes in the magnitude and phase of the transmission are modeled by a second-order low-pass system where the break-frequency increases and the damping ratio and low-frequency magnitude decrease with muscle contraction. The transfer function with maximum tensor contraction had a break frequency of 2.5 kHz with a damping ratio of 0.31, while the stapedins maximum contraction gave a breakfrequency of 1.57 kHz and a damping ratio of 0.71. These transmission changes are accounted for the most part, in the model, by a decrease in compliance of the middle ear, but there are also increases in resistance and inertance over the flaccid muscle state. AI3. Animal Exposure to Infrasound. D•,•m[ L. JoR•so•, 6570th Aerospace Medical Research Laboratory, Wright-Palterson Air Force Base, Ohio 45433.--The AMRL dynamic pres-sure chamber (a hydraulic device that produces intense infrasound) recently became operational. Preliminary to human whole body exposures, a variety of experiments with animals are being performed in o?der to evaluate physiological limits. A monkey, a young baboon, and six dogs of various sizes anestheti2ed with pentob. arbital were exposed from 1 to 4 h at the maximum levels the chamber is capable of producing (172.5 dB from I to 8 Hz and falling off 7.6 dB/oct to 158 dB at 30 Hz). EKG and respiratlou rate (via chest impedance measurements) were recorded. The only observed physiological effects were a decline in respiration rate and some reddening of the tympanic membrane. Except for three of the dogs, these animals were then given exposures in which they were not anesthetized. Exposure levels were gradually increased until all animals received the maximum chamber SPL for 1-14 h. Their behaviors were subjectively observed to be normally calm and occasionally restless. At no time did the animals appear in discomfort or show signs of nystagmus or dizziness. The lack of adverse results of these high exposure levels will be discussed. averaged holography has been successfully employed for obtaining high-contrast vibratory patterns of the tympanic membrane [Khanna and Tonndorf, J. Acoust. Sac. Amer. 41, 1904 (1972)]. Nevertheless, this technique has two restrictions: (1) the time delay due to the photographic processing of the holographic plates and (2) its essential inability to give phase information. Attempts to employ real-time holography [Tonndorf et al., J. Acoust. Sac. Amer. 46, 106 (1969)] for the same purpose failed because of (a) its inherent low fringe contrast and (b) its sensitivity to slow, quasi-de, membrane motions. Real-time holography that includes strobing [-Archbold and Ennos, Nature 217, 942 0968)] markedly improves the image contrast, as will be demonstrated on an earphone diaphragm. It also gives both amplitude and phase information. Additional phase modulation [Aleksoff, Appl. Phys. Lett. 14, 23 (1969)], as will also be shown, permits removal of the 180 ø phase ambiguity. This latter combination holds good promise for application to measure•nents on biological membranes. [Supported by several NIH grants.] 93101.--This method is based on the acoustic tube model of the vocal tract in which the tube is divided into a finite number of sections with equal lengths. The volume velocity is defined in each section. Input impedance at the front end of the tube (corresponding to the [ips) can be computed as the ratio of the pressure and the volume velocity there, providing that the volume velocity and the pressure are continuous at each boundstry between two adjacent sections. This input impedance is shown to be of the form D(•-)/G(•), where D(•-) and G(z) are polynomials in •-•. It is also shown that D(v_) and G(z) are con-The Journal of the Acoustical Society of America 293 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA structed as a difference and a sum, respectively, of two polynomials whose coefficients can be determined from the reflection coefficients of the acoustic tube model. Since a method for obtaining the reflection coefficients from the speech wave is already established [H. Wakita, SCRL Monogr. No. 9 (july 1972)], D(a) and G(z) can thus be obtained from the speech wave. Input impedance singularities obtained with area functions for five Russian vowels by Fant were in very good agreement with Mermelstein's results •J. Acoust. Soc. Amer. 41, 1283-1294 (1967)]. [The Office of Naval Research supported this work.] B2. Experimental Determination of the Area Function of a Lossy, Dynamically Varying Vocal Tract. M. M. SoNora, Ball Laboratories, Murray Hill, New Jersey 07974.--During the last year we have made acoustic impulse-response measurements at the lips while the vocal tract is moved as in normal speech. The experiment will be d•scribed and moves will be shown of the area functions reconstructed from the measurements. A method will be presented for estimating the mechanical impedance of the walls of the vocal tract. It will be shown that the reconstructed areas are significantly improved if the walls, instead of being assumed rigid, are assumed to have this estimated impedance. B3. Models of Articulatory Dynamics. C. H. COKER ANO C. P. BROWStAN, Bell Laboratories, Murray Hill, New Jersey 07974.--W'e present comparisons between the x-ray data of R. A. Houde [PhD Thesis, Univ. of Michigan (1967)] and actions of a dynamic articulatory model. The data can be fitted in two ways: (1) a model with minimum number of degrees of freedom, but with time-varying "characteristic filters" (Coker and Fujimura, J. Aconst. Soc. Amer. 40, 11(A) (1966)]; or (2) one in which different speeds of an articulator are produced by additional "characteristic variables" that would be redundant in the static case. The phe- nomenon that the constriction tends to move forward during /g/was suggested by Houde to result from pressure buildup in the enclosed cavity. We treat the effect as a peculiarity in "programming" of/g/. Horizontal motions toward /g/from front vowels are commanded 50 msec early, from back vowels, 50 msec late, thus producing a circular Lissajous pattern of motion. The dilemma of cause and effect (whether continued voicing forces tongue-body movement, or whether movement is explicitly commanded, to sustain voicing) leads to interesting questions when we attempt to generalize to other phonemes. Does circular motion occur in nasals and voiceless stops as well as/g/? Does the tendency for/g/to alevoice in some languages derive from differences in tongue control? These and other topics are discussed. B4. Nonlinear Inverse Filtering. MaRT•N ROTHENBERG, .--It has been shown by Flanagan and Landgraf [tEEE Trans. Audio Electroaconst. 16, No. 1, 57-64 (1968)-] that in the transformation between glottal area and glottal volume velocity during voiced vowels, the effect of the interaction between the acoustic impedance of the glottis and that of the supraglotta[ vocal tract cannot always be neglected. When there is such interaction, the glottal-supraglottal acoustic system must be considered a nonlinear system with time-varying parameters. Thus, any inverse-filtering process designed to extract the glottal area waveform from measurements of supraglottal pressure or air flow must also be nonlinear. This paper reports initial efforts to determine the conditions under which a nonlinear inverse-filtering process exists that will yield a function directly related to glottal area from recordings of oral volume velocity, and how such a nonlinear inverse filter could be implemented. ARTHUR S. ABRAMSON,• Haskins Laboratories, New Haven, Connecticut O6510.--Multichannel EMG recordings were made of the instrinsic and extrinsic laryngeal muscles during production of intervocalic labial stops of five phonetic types: explosive voiced inaspirate, implnsive voiced inaspirate, voiced aspirate, voiceless inasoirate. and voicele• a•pirate_ The recorded data, computer processed to obtained average EMG values, indicate that abductor and adductor muscle groups follow coordinated patterns of activity corresponding to opening and closing of the glottis. In particular, the interarytenoid and posterior cricoarytenoid muscles showed reciprocal patterns both in degree and timing of activity. In addition, the sternohyoid showed marked activity for the implosive stop, presumably correlated with an abrupt lowering of the larynx. In a second experiment using the same speaker and the same syllables, motion pictures of the glottis were taken by means of a flexible fiberscope. The overall conclusion suggested is that active adjustments of the glottis in terms of coordinated muscle activity, and the timing of this activity 2½:)4 Volume 53 Number I 1973 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA relative to supraglottal events, are the decisive factors by which the various stop consonant types are differentiated. Laboratories, Nero Haven, Connecticut 06510.--Aerodynamic forces require a vocal tract volume increase subsequent to oral cavity occlusion if voicing is to proceed through stop consonant closure. Electromyographic recordings of pharyngeal musculature were obtained for three subjects during the production of the six stop consonants of English in controlled phonetic environments. In addition, simultaneous electromyographic recordings and fiberscopic motion pictures were obtained for one subject producing a subset of the total utterance set. Each subject shows differences in the pattern of cavity enlargement for the voiced stops. One subject shows increased levator painting and sternohyoid activity, and demonstrates greater velar elevation (determined from the motion pictures} for voiced stops as compared with voiceless stops. A second shows decreased activity of the pharyngeal wall musculature along with increased activity of the sternohyoid for the voiced stop cognates. The third subject exhibits a composite of the activity patterns of the first two subjects. The data support earlier suggestions that pharyngeal expansion must be due, at least in part, to positive muscle activity. They also indicate that there may be intersubject variation of actuating mechanisms while the articulations are perceived as equal. the lower lip in the anterior-posterior and inferior-superior dimensions were recorded along with EMG activity from the orbicularis otis inferior (OOl), depressor labii inferior (DLI), and mentalis (M). Observations of activity in these muscles in relation to simultaneous displacement, velocity, and acceleration of lower lip movement suggest that (1) DLI and OOI act primarily to apply forces in the inferior and superior dimensions, respectively; (2) mentalis is a primary force for protrusion of the lower lip; and (3) the lower lip can be characterized, in a preliminary way, as a simple second-order mechanical system. The implications of the technique and the specific findings will be discussed in relation to development of an analog computer model of the labial-mandibular mechanical system. [Research was supported in part by grant from NIDR.] B10. Activity of Some Extrinsic and Intr/nsic Tongue Muscles in the Articulation of American English Vowels. KATHERINE S. Hnsgm* nNo LawREnCE J. RAPHAEL,• Haskins Laboratories, New Haven, Connecticut 06510.--Most previous electromyographic studies of tongue muscles have been limited to those extrinsic muscles which are easily accessible: the genioglossus and palatoglossus. Recent experiments have provided access to the styloglossus, among the extrinsic muscles, and to the intrinsic fibers of the tongue. Thus, a fuller picture of muscular synergisms in the positioning and shaping of the tongue is beginning to appear. This stndy reports findings from three subjects who spoke lO American English vowels in a labial consonant frame preceded by schwa. All electromyographlc activity was recorded from hooked-wire electrodes inserted into the various muscles by means of hypodermic needles. The results reveal as many differences as similarities between the articulatory strategies of the subjects. I t appears that the similar articulatory configurations that underlie the linguistically relevant acoustic structures of the vowels can be achieved by a variety of muscular patterning. [This research was supported by the National Institute of Dental Research.] D M. J. ]]ARRETT, University of Adelaide, .4 ustralia.--Recording eq nipmerit was transported to ¾uendumu, N. T., Australia, to obtain data on tongue and lip activity of aboriginals during speech and swallowing. Strain gauge pressure transducers were fitted into custom constructed plates to be placed in the speaker's mouth to record tongue and llp contact at several locations. Eighteen speakers whose native language is Walbiri acted as subjects. Eight prerecorded Walbiri words and four nonsense words, five repetitions each, were presented to the subjects. These tokens contained three of the Walbiri modifications of the phoneme /t/ situated intervocalically in each word. Distinct articulation patterns of both tongue and lips were found for the three phoneroes regardless of whether they were located in meaningful or nonsense words. Furthermore, pressure patterns for the phoneme most like the American language/t/were very similar to patterns for American speakers. This was true even though tongue and lip movements during swallowing were quite different from Americans. [Kenneth Hale assisted in preparing the speech stimulus. Support from the Fulbright program, NIDR, and Southern Society of Orthodontists is gratefully acknowledged.] BI2. A Two-Dimensional Strain Gauge Transducer System for the Lips and Jaw. J. H. ABss n•o B. N. GtLn•ar, Speech Research Laboratories, University of Washington, Seattle, Washington 98195.--A strain gauge transduction system was designed and constructed for simultaneous observation of the movements of the upper lip, lower lip, and jaw in both inferior-superior and anterior-posterior dimensions. Empirical verification of the system's structural loading factor, frequency response, linearity, and phase response suggests that it provides a favorable alternative to earlier lip and jaw monitoring dewces. Some examples of the two-dimensional multistructure movement patterns obtained with this device will be provided and discussed. [Research supported in part by NI DR/grant.'l BI3. Intraoral Air Pressure Correlates of Lip Occlusion for Bilabial Stop Consonants. THol•._ns SHIPP, Speech Research Laboratory, Hospital, San Francisco, California 94121.--The purpose of this procedural study was to determine if a oneto-one correspondence existed between the intraoral pressure curve and complete lip closing and opening for bilabial stop consonants. The faces of two subjects were photographed at high speed (250 fps) in simultaneous anteroposterior and lateral views as they produced a series of words with/p/and /b/, the midvocalic consonants of interest. A timing signal synchronized the film with the physiologic-acoustic record. The Journal of the Acoustical Society of America 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA Results showed that the onset of the intraoral air pressure risc coincided with the moment of complete lip closure while initial lip opening was coincident with the steep fall in intraoral air pressure. These relationships obtained regardless of consonant voicing or stress position, or whether the intraoral catheter was partially obstructed. BI4. Some Relationships between Vocal Effort and Intraoral Wright and Colton [J. Acoust. $oc. Amer. 51, 141 (1972)] described a power function between vocal effort and SPL that was concave downward with the knee of the function occurring apparently at the subject's most comfortable effort level. A similar function was noted for effort and fundamental frequency. In this study, a similar paradigm was utilized to explore the relationship between effort and intraoral air pressure. Vocal effort for the CVs /d•/and /ta/ was measured by magnitude estimation and production; intraoral air pressure was sensed with a tube-transducer system. Minimum, most comfortable, and maximum effort levels were also determined. The results show that vocal effort is a power function of intraoral air pressure. Furth_rmore, the function shapes were very similar to those reported by Wright and Colton; the change of slope tended to occur at the most comfortable effort level. Males tended to show the typical function; females tended to display a more straight function. These results tend to suggest the possible existence of two mechanisms involved in varied effort levels, since air pressure rises more rapidly below comfort level than above. .--Fine-wire-inserted electrodes were placed in the right and left palatoglossus muscles of 14 subjects. Two to four simultaneous placements were accomplished for each subject. Electrom¾ographic signals were recorded while each subject produced a speech sample designed to consider palatal and lingual movements. The data strongly suggest that, while palatoglossus function for the nonspeech act of swallowing is highly consistent within and between speakers, its specific function in speech production is less consistent. !n some subjects, the palatoglossus appears to function to actively lower the palate for nasals and at the end of utterances, while for other subjects it does not. In some subjects activity appeared related either to tongue movements or to stretch reflex. Finally, within any one subject, function was often variable. The data are discussed primarily with regard to palatoglossus function, although other aspects, i.e., its variability, which will be discussed in detail in subsequent papers, are also mentioned. Invited Papers (30 minutes) CI. A Review of Progress and Applications in Acoustic Microscopy. L. W. KESSLER, Research Department, Zenith Radio Corporation, 6001 H'est Dickens Avenue, Chicago, Illinois 60639.--Acoustic microscopy is a relative newcomer to the field of acoustic imaging which will allow the discrimination of micron-size structural detail and will render mechanical microstructure directly observable. Because of the unique characteristics of acoustic wave propagation in materials, potential wide areas of application are anticipated in both the physical and biological sciences. This talk will present a discussion of recent developments in acoustic microscopy techniques and applications. The present efforts to develop experimentally useful systems employ optical methods of sound amplitude detection through various means of coupling. The desired acoustic pattern can be displayed as a holDgram or as a conventional image. Further, phase contrast and dark field techniques are also possible. Thus far, resolution better than 10 t•m has been reported, and it is reasonable to expect that the resolution will soon be improved to the point of equivalence to optical microscopy, viz., about I t•m. Comprehensive investigations into possible applications of acoustic microscopy are somewhat restricted at present because of the unavailability of a suitable instrument; however, during the course of preliminary investigations, various interesting and meaningful contrasts have been demonstrated between acoustic and optical micrographs of the same specimens. These will be discussed in the context of their being the first such comparisons to be made rather than in the context of their being definite applications of acoustic microscopy. C2. Real-Time Ultrasonic Imaging by Bragg Diffraction. G. WADE, Department of Electr&al Engineering, University of California, Santa Barbara, California 93106.--Bragg diffraction is one of several principles presently being examined in research to produce optical images of objects irradiated by ultrasound. !n this method, laser light is diffracted from the scattered ultrasonic wavefronts as originally predicted by Brillouin in 1921. Historically, some of the first experimental attempts to use ultrasound for imaging were made by Sokolov in his Leningrad laboratory more than 40 years ago. One of the approaches he employed was remarkably similar to the approach presently being pursued 296 Volume 53 Number 1 1973 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA and suggested in 1966 by Korpel of Zenith. In our laboratory, we have carried out experiments involving sound frequencies of 15, 18, and 25 MHz and more recently 3.6 MHz. The images obtained at the higher frequencies are at least comparable to those of competing ultrasonic methods. At the lower frequency, special care must be taken to avoid interference between the image beam and the undiffracted light. This paper will discuss the practical problems encountered and will present theorectical calculations to compare several competing approaches presently being pursued. C3. Piezoelectric Arrays. R. K. M UgLLER, Bendix Research Laboratories, South field, Michigan 48076.--The first practical piezoelectric array was demonstrated by LangeviA early this century. It was a composite quartz transmit/receive unit for underwater search and surveillance. A wealth of new piezoelectric materials have since been developed. Sophisticated array processing techniques evolved and became practical with increasing speed and capacity of digital computers. These developments led to the present wide range of piezoelectric arrays with widely differing design objectives. A general survey of the state of the art will be given, and, as a specific example, some design features of a 96X96 holographic receive array presently under construction will be discussed. C4. Condenser-Transducer Arrays for Recording Acoustic Holographic Data in Real Time. A. K. NIGAI•, Bell Laboratories, Murray Hill, New Jersey 07974.--Two-dimensional transducer arrays consisting of a mosaic of condenser-microphone elements appear to be ideal acoustic analogs of the photographic plate for recording holographic data in real time. Such transducer arrays, employing either external or electret biasing, are reviewed in the present paper. In particular, two relatively simple and inexpensive designs [see for example A. K. Nigam, K. J. Taylor, and G. M. Sessler, Acoustical Holography, Volume 4, G. Wade, Ed. (Plenum, New York, 1972), pp. 173-194] are described in detail. Simplicity of tiesign is achieved by using a single solid-dielectric diaphragm, which is shared by a large number of microphone elements of the array, and by employing sequential data sampling, which eliminates expensive repetition of similar signal-processing equipment for each element of the array. Electrical and acoustical characteristics, such as interelement cross talk, element sensitivity, frequency range of operation, and the real-time capability for the two array designs are reported. These are found to compare favorably with the characteristics for the more conventional piezoelectric arrays. Acoustic images made with 16X 16 element prototype array• of the present design axe also discussed. C5. The History and Current Status of Liquid-Surface Acoustical Holography. BvRo• B. BREt•OEN, Holosonics, Inc., Richland, [['askington 99352.--The interaction of acoustic energy with a free liquid surface provides a means for rapid formation and readout of an acoustical halogram. Although a twostep holographic process is possible, involving recording the liquid•urface halogram on a photographic transparency, the real-time imaging capabilities are of most interest and provide the basis for all of the current use of equipment in industrial testing and biological imaging. The use of acoustic lenses to focus the object field of interest into the halogram is particularly useful for achieving good resolution. Industrial test applications and imaging of biological systems in real time are best illustrated using video tapes or motion pictures. C6. Summary of Progress and Future D/rectious in Acoustical Holography. A. F. METHERELL, McDonnell Douglas Corporation, Actran Industries, Inc., Manravia, California 91016.--The author will summarize the papers presented by the preceding invited speakers and review other developments in the field. Current problems and directions for future progress will be discussed. .--Fundamental statistical parameters used to describe stationary random vibrations are viewed with emphasis on those parameters of special concern in structural response and failure prediction problems. Included in the review are correlation and spectral density functions, instantaneous and peak value probability density functions, arbitrary level crossing statistics, and elementary considerations in the first passage problem. The relevance of the various statistical parameters to the prediction of structural fatigue and extreme value failures, The Journal of the Acoustical Society of America 297 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA assuming simple failure mechanism models, is introduced in qualitative terms. Both theoretical and experimental results are displayed to illustrate important relationships. Special attention is given to the importance of underlying assumptions inherent in classical applications, in particular, the excitation normality and system llnearity assumptions. Data are presented to demonstrate the impact of common nonlineartries on such response parameters as the instantaneous and peak value probability density functions. Finally, the importance of the stationarity and associated constant parameter system assumptions are discussed from a practical viewpoint. Illustrations are included to clarify the types of errors that result when nonstationary random excitations and responses are analyzed as if they were stationary. D2. Fatigue and Crack Propagation Analyses under Stationary Random Excitation. H. A. LEYBOLD, An accurate analytical method for predicting the fatigue life of an aircraft structure under actual operating conditions is not a reality today. Four maior parameters (i.e., material behavior, environment, structural configuration, and operational loads) plus the three phases of the fatigue process (i.e., initiation, crack propagation, and fracture) are involved in the prediction process and attest to the complexity of the problem. In addition, each parameter has its own statistical variability, which further complicates the problem. Even when treating each of the variables as independent events, the prediction process is still a complex one. This paper will deal with only one of the variables involved in the overall prediction process, namely, operational or random loads. Many investigators have proposed techniques for predicting life under random loading--with varying degrees of success--based on experiments, empirical rules, and/or past experience. The most noteworthy of those techniques are reviewed, and their capabilities and limitations assessed. The prediction of crack growth in aircraft structures is also of interest from a safety and reliability standpoint, as well as for setting up inspection and maintenance schedules. Current crack-growth prediction techniques, which incorporate fracture mechanics methods, are reviewed and assessed. A bibliography of pertinent references is included. D3. First Passage Analyses under Stationary Random Excitation. J. T. P. YAO, School of Civil Engineering, Purdue University, Lafayette, Indiana 47907.--A structure fails whenever its response to excitation reaches one or more limiting values. Structural responses include deformations and internal forces, of which the limiting values are based upon various failure criteria for the material. The failure probability of a structure subjected to random excitation can be found as the first passage probability of the response process across the most severe limiting strength values or deformation barriers. This problem can be solved in principle when the structural response is represented by a Markov process. However, exact solutions are available only for some first-order Markov process. Consequently, approximate methods have been suggested by various investigators. In this presentation, an attempt will be made to summarize and review the Potsson approximation with several independence assumptions, two-state Markov process assumption, clump-size estimation, use of an equivalent firstorder Markov process or a renewal process, simulation and numerical diffusion, upper and lower bounds, nonapproaching excursions, and the principle of maximum entropy of the total number of excursions. .--Random loads acting on structures can be placed into two broad categories. Into the first category belong loads with large numbers of repetitions such as those produced. by wind gusts, ocean waves, noise, boundary layer turbulence, fuel sloshing, or rough roads. Such loads are usually characterized by low-amplitude stationary or quasistationary random processes. Into the second category belong loads whose appearance is less frequent. Loads produced by sonic booms, earthquakes, ballistic impact, severe maneuver loads, hurricanes, tornadoes, and tsunamis are classic examples. These have short durations, often large amplitudes, and are governed by nonstationary random processes. While the two groups cannot be completely separated, the first types are usually responsible for the gradual deterioration of structural strength and those in the second class may produce ultimate load failures. Structural response to these random loads depends on basic material properties, as well as on the type of structure, connections, and support conditions. Because structural reliability implies a failure-free operating life, the definition of failure becomes an important parameter. Depending on the structure and its usage, partial failures in conjunction with alternate load paths require consideration. In order to achieve current structural failure goals of the order of 10 • to 10 -9, all the above statistically variable conditions should be considered together. Because of the high complexity involved, however, only individual parts of the problem have been successfully handled in the past. Both theoretical and experimental investigations of the complete problem will hopefully be understood in the near future. D5. Experimental Fatigue Results under Stationary and Nonstationary Random Vibration. S. R. SWANSON, MTS Systems Corporation, Minneapolis. Minnesota 55424.--There is a steadily increasing supply of interesting fatigue test result for materials under the action of random processes, especially in the area of stationary random loading. In the strictest sense, nonstationary random processes in fatigue should be considered quasistationary processes since the fatigue loading is nominally stationary over the long run to failure. It is possible to imagine nonstationary loading s over a complete fatigue life (such as the action of wear or steadily increasing damping in a fatigue test), but actual tests of this nature are not yet available. This paper surveys the field of stationary and quasistationary 298 Volume 53 Number i 1973 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA random loading subsequent to the author's 1968 state of the art paper on this topic. One of the most significant findings from this survey is the widespread use of repeated random loading sequences by research groups and working professional committees in interlaboratory test programs. The necessity to analyze service loadings carefully, to separate random and nonrandom aspects, is also dealt with in detail. Invited Papers (25 minutes) El. Coherence of Signals, Noise, and Reverberation in the Sea. R. J. UmcK, Naval Ordnance Labortory, Silver Spring, Maryland 20910.--Separated hydrophones in the sea show varying degrees of coherence, or waveform similarity, depending on separation, frequency, and kind of sound observed. Over the past 10 years, we have measured the phase coherence of different kinds of signMs, noise, and reverberation between vertically separated hydrophones. Such information is basic for the optimum design of arrays. This paper summarizes these measure•nents. When plotted against normalized separation the coherence as measured by the clipped correlation coefficient is found to lie, as it should, between the value of unity for a plane wave and a curve for isotropic noise; it depends on the vertical angle within which the sound arrives at the two hydrophones. The most coherent sonnds observed were signals in convergence zones; the least coherent, the reverberation received from great depths in the deep sea. .--With the support of the French Navy, a low-frequency sound propagation experiment was conducted to obtain attenuation coefficients in the Indian Ocean for the frequency range 200-10 000 Hz. The experiment was conducted along a 500-kin track, which was characterized by a broad sound channel with an axis depth of 250 m. The results are compared with previous measurements in the Red Sea ant{ Atlantic Ocean. fast field program (FFP) is used to study sound propagation in a deep ocean sound channel for the frequency range 1-200 Hz. Typical sound velocity profiles from the Atlantic and Pacific Oceans are used. Both the velocity profile and bottom depth are assumed to be invariant with range. The channel cutoff frequency is determined and the bottom loss contribu-tion to the measured values of attenuation is estimated. Comparison is made with recent experiments. ES. Long Range Acoustic Transmission Loss in the Northern Denmark Strait. D. L. BRAOLEV ANO G. M. CALVIN, Naval Ordnance Laboratory, Silver Spring, Maryland 20910.--Long range acoustic transmission loss measurements were made in the northern Denmark Strait area utilizing two aircraft. One aircraft flew prearranged tracks, dropping standard U.S. Navy explosive charges, while the second aircraft remained in the area of deployed calibrated sonobnoys, acting as a receiving platform. Received signals were recorded broad band aboard the monitoring aircraft. These broad-band recordings were analyzed by filtering, squaring, and integrating to obtain energy density in selected «-oct bands. The Weston values of source level for the explosive charges were used in the calculation of transmission loss. Transmission loss data for several octaves are shown as well as the results of calcu[atioos of a loss per unit distance factor [.J.D. MacPherson, J. Brit. 1 RE 26, 293 (1963)]. This factor is obtained by assuming spherical spreading to 1 kyd and cylindrical spreading thereafter and Contributed Papers (12 minutes) Fl. Abstract withdrawn. 300 Volume 53 Number I 1973 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA F2. The Design of a 360-Degree Symphonic Facility. CHRISTO-PhER JAFFE, Christopher Jaffe, Inc., Norwalk, Connecticut 06852.--[n 1971 the first 360 ø concert facility for a major symphony orchestra was completed at Ontario Place, Canada, as a summer home for the Toronto Symphony. This paper describes the physical and electroacoustic criteria developed to meet the program requirements, discusses the degree to which the criteria fulfills design objectives, and the response of artists and audiences to this intimate, less formal performance environment. The new 1460-seat Opera Hall at Indiana University has been widely acclaimed for its architecture, its advanced theater technology, and its acoustics for opera and concert. This paper describes the physical characteristics of the hall in general and its acoustical characteristics in particular. Both objective data and subjective evaluations of its opera and concert uses are presented and compared with design criteria and functional objectives. the effects of the system up to the source input (say a speaker) are totally removed, the speaker modification to the actual room impulse response is a difficult quantity to deal with. Because of the inherent rise time in any impulse response, the speaker impulse response is not minimum delay (or minimum phase) and hence an exact convolution inverse operator is not stable. Methods to deal with this are discussed and practical results from a Wiener filter approach are presented. [Supported in part by two grants from NASA.] F6. Design Practice Relating to Acoustics in Schools. W•I•L•AM K. CO•OR, TRACOR, Inc., Austin, Texas 78721, XNO RO•ER BENASUTTI, Conwed Corporation, St. Paul, Minnesota 55101.--A questionnaire survey of 401 architectural firms, completed F8. Effects on Speech Perception of Modifying the Impulse Response of a Small Room. D. A. B•Rr. rEV, T. H. CURtiS, ANO J. B. ALL•N, Bell Telephone Laboratories, Incorporated, Holmdel, New Jersey 07733.--A linear model of the ear as a parallel bank of filters and the image solution for room response are outlined. These models are used to predict the perception of speech under certain controlled variations in the impulse response of a small room. Using either a hardware digital filter or a computer simulation, room impulse responses have been measured, modified, and their effect on speech examined. The investigations included linearizing the phase of and truncating the impulse response, examining an all-pass filter w•th a real room phase characteristic and observing the effect of the time complement of a truncated impulse response. F9. Miniature Anechoic Room Design. W. M V•gaROCZ* ANO M. J. CttOCZgR, Ray W. Herri•k Laboratories, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907.--The design of a small portable anechoic room is discussed. The room was constructed with double wall vibration-isolated panels. The wall transmission loss was predicted using London's theory. The room suspension system was designed using a lumped-mass model for isolation from floor vibrations. The design of the room utilized 8-in.-Iong polyurethane foam wedges. Using an impedance tube, men-The Journal ot the Acoustical Saciety of America 301 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA 84TH MEETING ß ACOUSTICAl. SOCIETV OF AMERICA 11:00 G1-7. Industrial Noise in the Community--Current Views. L•.w•s S. GOOOFmEND, Morristown, New Jersey 07960.--Noise from industrial plants has continued to be a problem for both the plant managements and their neighbors. Several recent studies have indicated that the majority of persons in residential areas are exposed to ambients set by transportation noise sources. This is of little comfort to the immediate neighbors of an industrial plant whose noise dominates a small region surrounding the plant. Recent acceptance of the A-weighted sound level to rate noise, results of several Federal studies, and an evaluation of the Normalized Community Noise Equivalent Level (NCNEL) have changed the community-industry situation little, but prepare the way to develop workable methods for rating noise situations in a manner similar to the earlier Composite Noise Rating, but without measurement of the spectrum. Furthermore, the interrelationship of a community and its industrial neighbors appears to play a major part in the acceptance of the noise levels surrounding the plant. This leads to the conclusion that there is no universal method of rating community noise that will satisfy any given percentage of neighbors in a community without first determining attitudinal factors that can be applied in the noise evaluation as weighing factors. Further research is currently under way. This effort is critical since current work to reduce transportation noise may lead to a situation where industrial noise becomes dominant in the major portion of many more communities. 11:30 GI-8. The Citizen Response to Noise Since 1967. ROaoeRT A[oex Baao•, Executive Vice President, Citizens for a Quieter City, Inc., P.O. Box 7777, Ansonia Station, New York, New York 10025.--Since 1967, the citizen is on the offensive. He has learned how to intensify awareness of noise pollution. His educational techniques have become more sophisticated. Pressure points have been discovered and are being applied. Environmental noise is now being recognized by some acousticians and polluters. However, significant moves toward abatement have yet to be taken. While the hearing loss The Journal of the Acoustical Society of America •303 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA aspect of occupational noise is now being recognized in legislation, the nonauditory aspects are totally neglected. The citizen is, therefore, now including a concern for occupational noise while intensifying his battle against environmental noise exposure. The noise receiver is still asking the acoustician to move from measurement for the protection of vested interests to abatement for the sake of human interests. TUESDAY , 28 NOVEMBER 1972 EL DORADO EAST, 2:00 P.M. Session G2. Community and Vehicle Noise 90024.--In the first part of a two part study, indoor and outdoor measurements of jet aircraft noise were obtained at seven schools beneath the eastern approach paths to Los Angeles International Airport. At five elementary schools, the jet noise in the schoolyards ranged from 100 to 120 dBC and constituted a high risk of hearing damage for the young children. The frequency of jet aircraft overflights averages 1 per 2 rain for a total of over 200 per school day (8:30 A.M.-2:30 P.M.). The corresponding jet noise levels in the classrooms, 80% of which are not air conditioned or acoustically treated, ranged from 80 to 96 dBA, and caused total disruption of the communication and learning processes. An investigation of aircraft operation alternatives indicated that the noise could be reduced by 10 dB or more if engine power were reduced when the aircraft approached the school areas, or if the aircraft approached at higher altitudes and landed further to the west on the unused 6000-ft-long portion of the 12 000-ft-long runways. $8.--Existing airport noise prediction programs are incapable of dealing with complex flight paths and normal dispersion of flight paths due to variations in aircraft gross weight or pilot technique. A computer program that is capable of handling these problems has been developed, using an air traffic control simulation program as its base. The original air traffic control program is capable of very accurate simulation of aircraft motion in an airspace, including random deviations from assigned parameters and automatic meterlng of traffic using holds, delaying turns, etc. A grid of noise measuring points, of arbitrary extent, is superimposed on the airspace and constant recording of aircraft noise at each location is simulated. At the end of a "run," a contour plot of noise levels in the grid area is produced. Variations in traffic density, controller technique, traffic patterns, and runway use can be simulated, and the results of such variations conpared directly. 90024.--Measurements of police helicopter noise were made during surveillance flights over communities in several cities in the Los Angeles area. Small light observation-type helicopters (Hughes 269 and 300 and Bell 206) are used for emergency and surveillance work by the police departments of most cities in the Los Angeles area, and by the sheriff's departments in the southern California seven county area. These helicopters typically fly over the various communities several times each day and during the late evening hours. Operation of these helicopters at 500-to 1000-ft altitudes results in noise levels of 70-80 dBA in the residential communities. Helicopter flights over schools and colleges caused noise levels of 65-75 dBA inside the classrooms. This is 10-20 dB above,the maximran allowable limit of 55 dBA for acceptable speech communication in offices and classrooms. In the Santa Monica area, late uight flights and search patterns caused noise levels of 100-115 EPNdB over hospitals and convalescent homes. These levels are in violation of municipal noise codes and exceed the federal landing noise limits for new jet aircraft. G2-4. Exposure of Communities to Low-Frequency Noise from Aircrafts and Rockets. D. K•ao, U. ["EAR, M. BURNSTEIN, B. IRON, AND J. GOLDMAN, Mareash Applied Science Laboratories, Ness-Ziana, IsraeL--Data collections, in the low-frequency noise region (below 100 cps), in communities located near airports were analyzed for the purpose of volumetric coverage. The following factors, such as residential areas under influence, volume of noise, time of noise, and range of influence, have indicated the importance of these studies. Isosurfaces of SPL of jet planes at altitudes of up to 7000 ft are shells in the shape of pears, with the top directed towards the ground. The top covers a minimum area of 12 000 kmL The pearshaped envelope is pulled in the direction of the flight, and this produces a time delay and altitude dependence between the community exposure to radiated noise, and the instantaneous location of the plane. Typical time exposures for altitudes of 1000 to 7000 ft are 4S-74 sec. This low frequency does not raise complaints because of the human ear's limitations; nevertheless they might be harmful. Furthermore, infrasonic frequencies (4 cps and below), having energies of I00 dB and more, cover 10 000 kin: and have durations of up to 30 min. Studies of physiological effects on animals and humans are of importance in this field. If these frequencies are harmful or bothersome, the jet engines should be designed to dissipate these energies at higher frequencies which attenuate strongly and do not propagate long distances in the atmosphere. 304 Volume 53 Number 1 1973 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA G2-10. A Comparison of the Predicted and Actual "Noise Pollution Level" for Vehicular Traffic on Limited Access Highways. M. J. OSLAC, The Noise Control Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802.--A superhighway near a suburban community formerly connoted convenience and instant accessibility to job, recreation, shopping, etc. Today, land values are more often relating to environmental serenity. This awareness of highway noise has prompted Environmental Impact Studies prior to the final design of new highways. The surrounding environment must be protected at least to the extent of the recently adopted FHWA Policy and Procedure Memorandum 90-2, which for a 24-hour period sets the noise limits which may not be exceeded more than 10% of the time. While this may be a good starting point, the Policy lacks the requirement that a measure of the background be made. Robinson's Noise Pollntion Level (NPL) provides a more realistic value of annoyance from vehicular traffic in that it provides for inclusion of the background. It thus offers a possibly better guideline. The recent study described in this paper utilized the Lt0 and L00 values calculated from the NCHRP Report No. 117 to predict the NPL for four eastern United States communities adjacent to limited access highways. Measurements were made at the four sites and an exact NPL was calculated using the energy mean value and the standard deviation. An attempt was then made to correlate these values with community response questionnaires. These values were also compared to the Lio levels in PPM 90-2. The implications of using NPL in Environmental Impact Studies is discussed. Starting with the premise that intense aerodynamic mech-The Journal of the Acoustical Society of America 305 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA hisres are responsible for a significant fraction of the noise radiated by a "relatively smooth" tire rollling on a "relatively smooth" surface, experiments have been conducted to identify and quantify such mechanisms. The experiments, conducted on a passenger car vehicle equipped with rib-type tires, include flow visualization studies and fluctuating pressure measurements both in the vicinity of the tire-road interface and in the acoustic far field (i.e., with the microphone mounted at the end of a 5-ft boom). A unique technique, involving cross correlation between the near-field pressure and the far-field sound measured by the boom mounted microphone, yielded significant information on the distribution of acoustic sources in the vicinity of the tire. These measurements indicate that a strong unsteady flow field does indeed exist in the region immediately behind the tire-road interface, and that this unsteadiness makes a dominant contribution to the noise. Alternative models for the aerodynamic mechanism, based on Hayden's "air-pumping" hypothesis, and a newly advanced "vortex interaction" process, are described and compared. cal Engineering, Suite 3, 690 Number Three Road, Richmond, British Columbia, Canada.--A new approach to noise survey work emphasizes the importance of spatial and temporal noise level variations with less stress on frequency content. It is shown that a low cost sound monitoring package, Aweighted at the input stage, and with a dynamic range of 45 dB, yields adequate information on which to base a concise, statistical model of the acoustic landscape. Because of the low cost of individual terminal units, a large number of units may be operated over an extended land use area. This ensures that important spatial information is not lost. Such a detailed picture is not possible with the more conventional sequential (point to point) techniques that are normally employed. The format for a typical area-wide noise level survey is presented, and the usefulness of the data obtained to urban planners and legislators is briefly described. G2-13. In-Service Tire Vibration Investigation. perimental research program has been initiated to measure and correlate the sound and vibration spectra of in-service truck tires. The objective of this work is to obtain a detailed bank of tire sound and vibration data that will aid in a better understanding of tire noise generating mechanisms and how they are influenced by important parameters such as load, tread type, tread wear, and speed. --Molecular geometry is important in interpreting the properties of liquid crystals. In addition, the molecular packing in different liquid crystalline structures will be presented and correlated with the properties of the liquid crystalline state of matter. This information on molecular packing will be focused essentially on thermotropic liquid crystals, but some information will be presented on lyotropic ones. A brief synopsis of some of the most interesting applications of liquid crystals will be presented. H2. Visualization of Ultrasonic Waves Using Liquid Crystals. P. GRE•OSS, Department of Ophthalmology, New York Medical College, New York, New York 10029.--The search for a device that transfers acoustic wave information into equivalent light information began its rebirth after the first ultrasonic holograms were recorded on sohOsensitive plates in 1964/1965. About the same time, the heat sensitivity of liquid crystals which shows up in color was introduced to NDT to find flaws. Since when an ultrasonic image is projected onto a suitable absorbing material it is converted into a corresponding spatial temperature variation over the absorber, it is clear that by coating the absorber with a layer of liquid crystals the intensity distribution of the ultrasonic field will be visualized. Examples of this technique will be presented. In nematic liquid crystals, five electrooptic effects--dynamic scattering, voltage-controlled optical activity, fast turnoff mode, deformation of vertically aligned phases, and guest-host interactions•can be observed, all of which may be affected by ultrasonic waves. Therefore, they can be used to transfer acoustical wave information into light information. The birefringent properties of a new specially prepared liquid crystal cell (AOCC) offer a new real time acoustical-tooptical display, which can als be used to record ultrasonic holograms. The pluses and minuses of the AOCC will be discussed in connection with a short movie. H3. Liquid Crystals and Broken A general approach to the determination of the equations governing linearized hydrodynamics in systems with broken con-306 Yolume 53 Number 1 1973 84TH MEETING ß ACOUSTICAL SOCIETY OF AMERICA 12. Twenty Years of Medical Ultrasonic Imaging. JOHN M. REIn, Providence Hospital 5eaUle, Washington 981•Z.--Ultrasonic imaging systems are becoming important in medicine. Our growing understanding of fundamental acoustical-tissue interactions may contribute important new abilities. Absorption and velocity of the sound vary with the structure of tissue and together determine the resolution and penetration of any diagnostic system. The reflecting and scattering properties of tissues are little known although much can inferred from clinical studies. Quantitative work in scattering is only beginning. Imaging systems can be classified on the basis of their range-venus-depth resolution and scanning time-versus-complexity tradeoffs. Early pulse-echo scanners had such "new" features as real-time imaging and gray scale response. Many medical centers now use contact and waterbath scanners. Newer pulse-echo and CW systems require complex electronics that were not feasible before integrated circuits were available. A promising new area is use of special target properties to identify reflecting objects. For example, working systems identify the Doppler-shifted backscatter from moving blood to map areas of flow. Present systems are adaptable to such imaging techniques. The nonstationary rms response of single-degree-of-freedom linearly elastic structural systems to several classes of nonstationary random excitations are summarized and compared. Particular emphasis is placed on shot noise, time-modulated white and correlated noise, and evolutionary and segmented nonstationary excitations. The influence of both structural system and nonstationary excitation parameters upon rms response is evaluated. Approximate response approaches are discussed. J2. Spectral Representations under Nonstationary Random Excitation. Invited Papers (25 minutes) KI-I. Speech producing Abilities of primates and Human Evolution. DENNIS H. [•LATT, Massachusetts Institute of Technology, Cambridge 0•139, PHlbtr LI•DI•RMA•, Th• •rrtlwr•ity of Connecticut, Connecticut 06268, and Haskins Laboratories, New Haven, Connecticut 06510, ANO Et•MON•) S. Yale University School of •V[edicine, New Haven, Connecticut 06510.-•Comparative anatomic and acoustic studies of the supralaryngeal vocal tracts of living and extinct primates indicate that speech production has been an important factor in human evolution. The sounds of human speech make human language a rapid medium of communication through a process of speech "encoding." The presence of the human vowels/a/,/i/, and/u/facilitates this process. The supralaryngeal vocal tracts of
doi:10.1016/0013-7944(73)90064-7 fatcat:eue2d6byvre4zczgb7qi5np5vi