Does Earphone Type Affect Risk for Recreational Noise-induced Hearing Loss? Does Earphone Type Affect Risk for Recreational Noise-induced Hearing Loss?

Brian Fligor, Sc Director, Terri Ives
Over the past year, considerable media attention has been given to the potential risk of hearing loss associated with the use of portable music players. A study of output levels of portable compact disc (CD) players (Fligor and Cox, 2004) suggested recommendations for safer listening level and duration for consumers. Fligor and Cox (2004) also reported in-ear earphones produced higher sound levels than over-the-ear headphones at the same volume control setting. Based on this finding it was
more » ... mended that volume control settings and listening durations should be adjusted accordingly. A report at this conference on output levels of mp3 players (Portnuff and Fligor) describes similar findings, updated for the current generation of technology. We now know what portable music players and earphones of capable of, but how are these devices actually being used? This study describes how using different earphones in different background noise affected listening behavior. It also estimates the number of people who are potentially at risk for hearing loss from their portable music player headphones in different listening environments. Methods One hundred normal hearing doctoral students participated in a study of "chosen listening level" of music over earphones. Four different earphones styles were evaluated to see what affect they might have on students' listening behaviors: an over-the-ear Koss headphone KSC11, an in-the-ear Sony earphone MDREX51LP, an in-the-ear Etymotic Research ER-6i earphone, and the Apple iPod earbud. Research subjects had their hearing tested to confirm normal hearing, and chose a song from a list of current popular titles. Two of the earphones in this study (Sony MDR-EX51LP and the ER-6i) were manufactured to provide some amount of background noise isolation, while the other two earphones (Koss KSC11 and the Apple iPod earbud) were not manufactured to block out background noise. The amount of background noise isolation each of the four earphones gave each research subject was measured. The students were seated in an Audiology testing booth and different types of simulated and real-world noise conditions were played out through a speaker into the booth at different sound levels. The student was then signaled to turn on their music player and adjust the music to "where they like it". Those levels were recorded in the subjects' ear canal using a thin tube attached to a microphone, which fed the information out of the booth to a computer for recording. Some mathematical adjustments were made to the recordings to correct for the changes in level caused by the ear canal (this is so that levels can be directly compared to governmental noise limits established for loud sounds in the environment, such as factory noise filling a room). This was repeated in random order for each earphone type, noise type, and noise level. Average Chosen Listening Level 50 55 60 65 70 75 80 85 90 95 20 30 40 50 60 70 80 90 Background noise Level (dBA)