Modeling the External Ear Acoustics for Insert Headphone Usage

Although the acoustics of the external ear has been studied extensively for auralization and hearing aids, the acoustical behavior of insert headphones is not equally well known. It is laborious to measure the sound pressure at the eardrum for individual insert headphone users. The present research focused on the effects of the outer ear on sound pressure at the eardrum during insert headphone listening. The main factors of interest were the length of the canal and the impedance of the eardrum. Ear canal simulators and a dummy head were constructed, and measurements were also performed with human ear canals. The study was carried out both with unblocked ear canals and when the canal entrance was blocked with an insert earphone. Special insert headphones with in-ear microphones were constructed for this purpose. Physics-based computational models were finally used to validate the approach. The different methods used to investigate the pressure inside the ear canal gave similar and accurate results. Hence the modeling techniques proved to be useful in estimating the pressure frequency responses at the eardrums of individual insert headphone users.