The main objective of this study was to determine the influence of listening environment and earphone style on the preferred-listening levels (PLLs) measured in users' ear canals with a commercially-available MP3 player. It was hypothesized that listeners would prefer higher levels with earbud headphones as opposed to over-the-ear headphones, and that the effects would depend on the environment in which the user was listening. A secondary objective was to use the measured PLLs to determine the permissible listening duration to reach 100% daily noise dose.
There were two independent variables in this study. The first, headphone style, had three levels: earbud, over-the-ear, and over-the-ear with noise reduction (the same headphones with a noise reduction circuit). The second, environment, also had 3 levels: quiet, street noise and multi-talker babble. The dependent variable was ear canal A-weighted sound pressure level. A 3 × 3 within-subjects repeated-measures ANOVA was used to analyze the data. Thirty-eight normal hearing adults were recruited from the Faculty of Rehabilitation Medicine at the University of Alberta. Each subject listened to the same song and adjusted the level until it “sounded best” to them in each of the 9 conditions.
Significant main effects were found for both the headphone style and environment factors. On average, listeners had higher preferred listening levels with the earbud headphones, than with the over-the-ear headphones. When the noise reduction circuit was used with the over-the-ear headphones, the average PLL was even lower. On average, listeners had higher PLLs in street noise than in multi-talker babble and both of these were higher than the PLL for the quiet condition. The interaction between headphone style and environment was also significant. Details of individual contrasts are explored. Overall, PLLs were quite conservative, which would theoretically allow for extended permissible listening durations. Finally, we investigated the maximum output level of the MP3 player in the ear canals of authors 1 and 3 of this paper. Levels were highest with the earbud style, followed by the over-the-ear with noise reduction. The over-the-ear headphone without noise reduction had the lowest maximum output.
The majority of MP3 players are sold with the earbud style of headphones. Preferred listening levels are higher with this style of headphone compared to the over-the-ear style. Moreover, as the noise level in the environment increases, earbud users are even more susceptible to background noise and consequently increase the level of the music to overcome this. The result is an increased sound pressure level at the eardrum. However, the levels chosen by our subjects suggest that MP3 listening levels may not be as significant a concern as has been reported recently in the mainstream media.
Recently, the hearing risks associated with MP3 players have garnered significant attention in the mainstream media. This investigation was designed to address the influences of 2 specific variables (the listening environment and the type of headphone used) on the chosen listening levels of a group of young normal-hearing adults. We found that, in noisy environments, there was a tendency to listen at higher levels with all types of headphones. However, the influence of the noise depended on what type of noise it was and what type of headphone was used. In street noise, subjects chose the highest listening levels with the in-the-ear headphones (earbuds). Over-the-ear headphones, especially those with noise reduction capabilities resulted in subjects choosing lower levels in the background noise conditions. Interestingly, estimates of maximum allowable daily noise doses were fairly conservative for most conditions.
Department of Speech Pathology and Audiology (W.E.H., J.M.R., R.A.S.), University of Alberta; Craniofacial Osseointegration and Maxillofacial Prosthetic Rehabilitation Unit (COMPRU) (W.E.H., J.M.R.), Caritas Health Group, Edmonton, Canada.
Address for correspondence: William E. Hodgetts, Department of Speech Pathology and Audiology, University of Alberta, Edmonton, Alberta, Canada, T6G 2G4. E-mail: email@example.com
Received April 10, 2006; accepted November 29, 2006.