Objectives: To measure the output sound pressure levels of personal music systems and evaluate their effect on hearing.Methods: Output sound pressure levels at preferred volume settings and listening environment were measured using a manikin. Effects of personal music system use on hearing were evaluated using pure tone audiometry (in conventional and extended high frequency ranges), transient evoked otoacoustic emissions, syllable identification in noise, intensity discrimination, frequency discrimination and temporal modulation transfer function.Results: Results showed, alarmingly, that large proportions of young adults are using personal music systems at levels higher than the safety limits set by regulatory bodies. Individuals who listened to personal music systems at levels higher than 80 dB LAeq exhibited poorer extended high frequency thresholds, reduced transient evoked otoacoustic emission amplitudes, poorer frequency discrimination, reduced modulation detection thresholds at 32 Hz modulation frequency, and reduced syllable identification in noise at -5 dB signal-to-noise ratio. Listening levels were significantly correlated with extended high frequency thresholds and transient evoked otoacoustic emission amplitudes.Conclusion: These results suggest that listening to music through personal music systems at higher volume levels may be hazardous to hearing.