Estimating Individual Sound Pressure Levels at the Eardrum in Music Playback Over Insert Headphones

In binaural sound reproduction and in many audiometric applications it is important to know the exact sound pressure at the eardrum of a listener. However, measuring sound close to the eardrum is often difficult and inaccurate in practice due to the physical size of the microphone capsule and cabling, and their variation in placement inside the ear canal. In this paper, insert headphones with in-built miniature microphones and acoustic modeling to estimate individual eardrum sound pressure from the microphone signals were used in assessing music playback levels. Eight listeners participated in the experiment and based on the results, the levels used did not pose an immediate threat to the hearing health. Adding noise to the listening environment increased the playback levels, and if listened to a longer duration, these could have a detrimental effect on hearing. Furthermore, even though the individual coupling of the insert headphones was accounted for, large inter-individual differences in playback levels were observed.