iii APPENDIX A -The Secure Voice Conferencing Facility 33 APPENDIX B -A Resource Allocation Task 43 NETWORK SPEECH PROCESSING I. INTRODUCTION AND SUMMARY The Network Speech Processing effort funded by DCA consists of three major tasks focusing on secure voice conferencing, narrowband speech digitizing algorithms, and bandwidth efficient communications. Each of these tasks is directed to particular problems associated with AUTOSEVOCOM II and/or the design of future DCS. The secure voice

more »

... ing effort is concerned with the analysis and simulation of various conference bridging and switching configurations, control protocols, delays, and conference sizes. The effort in speech algorithms is presently directed toward the severe problem of wide speaker dynamic range which causes distortion in narrowband speech digitizers (specifically LPC vocoders). Solutions to this problem will also enhance the quality of speech realized from LPC-CVSD and CVSD-LPC tandem connections. The ongoing study of bandwidth efficient systems, in particular the packetized virtual circuit (PVC) approach, is yielding valuable data on circuit and system utilization and efficiency, network delays, and various sources of distortion. The following sections describe progress to date on each of the three contract areas. The conferencing section discusses the large conference facility designed to simulate all the conference configurations pertinent to DCS, as well as outlining the human factors evaluation issues. The speech algorithm section discusses present results in automatic-gain-control experiments applied to the LPC vocoder. Finally, the bandwidth efficient communications section presents results to date on all the PVC studies performed by Lincoln Laboratory. II. SECURE VOICE CONFERENCING