Date of Degree


Document Type

Capstone Project

Degree Name





Brett A. Martin


Background: Noise-induced hearing loss, hearing loss caused by exposure to loud sounds, affects individuals of all ages. One cause of noise-induced hearing loss is listening to music at high intensities on personal listening devices, such as the iPhone. The aim of this study was to compare the intensity of music in the ear canal when presented in quiet at multiple volume settings through 4 different headphone styles (2 over the ear and 2 earbuds) to the intensity of the music in the ear canal when presented in typical subway noise. The results were used to determine recommended listening durations for the iPhone based on earphone style and music intensity in quiet listening environments and on the subway.

Method: This study used an iPhone 6s to present a 30 second clip of the 2015 #1 song “Uptown Funk” by Mark Ronson, featuring Bruno Mars (Billboard, 2015). The output of the iPhone was fed to a Zwislocki coupler inserted into the left ear of Knowles Electronic Manikin for Acoustic Research (KEMAR) and RMS sound intensity was measured using a sound level meter. A total of 4 different headphones were used to present the music clip in two conditions (in quiet and in 80dBA of subway noise). The music was played at 4 different iPhone volume settings: 25%, 50%, 75% and 100% of the maximum volume. Measured intensities were then compared to the WHO and EPA allowable listening levels of a 24-hour period in order to determine safe listening duration as a function of music intensity and background noise.

Results: In terms of volume setting across all 6 headphone conditions, 25% of maximum volume had recorded peak amplitudes ranging from 52.8dB SPL (Sony ZX series) to 82.6 dB SPL (PowerBeats Plugged) in quiet and 76.4 dB SPL (Beats Studio) to 85.8 dB SPL(Apple EarPods Plugged and Sony ZX Series) in noise. 100% of maximum volume had recorded peak amplitudes ranging from 93.3 dB SPL (PowerBeats Unplugged) to 119.4 dB SPL (Beats Studio) in quiet and 94.3 dB SPL (PowerBeats Unplugged) to 119.4 dB SPL (Beats Studio) in noise. In terms of the difference in dB SPL between quiet and noise conditions, the in-the-ear earbuds had a range from 0 dB SPL (Apple EarPods Plugged at 100% volume) to 30.9 dB SPL (Apple EarPods Unplugged at 25% volume). For the over-the-ear headphones, the differences in dB SPL between the quiet and noise conditions ranges from 0 dB SPL (Beats Studio at 100%) to 33 dB SPL (Sony ZX Series at 25%).

Recommended listening durations decreased as volume setting increased, as would be expected. At a volume setting of 25%, listening durations were longest--at least 8 hours for all headphones in quiet or in noise. At a volume setting of 100%, however, listening times decreased, ranging from 1 hour to 14 seconds, depending on headphone.

Conclusions: In subway noise, the intensity of the music plus the noise reached potentially damaging levels. Some earphone styles offered more protection from the subway noise than others. For the over-the-ear style, the Beats Studio headphones offered the most protection.

Although the SONY headphones provide longer listening durations in the presence of subway noise, especially at 75% and 100% of maximum volume, less of the signal reaching ear level was the desired music. For the in-the-ear style, the PowerBeats, when well-sealed in the ear canal, offered the most protection from the subway noise. The PowerBeats also yield the longer safe listening times. Overall, the over-the-ear style headphones provide more protection and longer listening durations in the presence of subway noise compared to in-the-ear earbuds. This study provides data that could be used to promote awareness regarding the dangers of listening to music at loud intensities for long durations, especially in the presence of background noise.