There are several challenges in predicting the pressure response of a sound source at the eardrum. Placing microphones at or closely near the eardrum is challenging and not feasible for daily use. In-ear headphones outfitted with microphones can provide an estimation of the pressure at eardrum by measuring the pressure at the headphone microphone and by using a transfer function of the pressure at the microphone to the eardrum. The accuracy of the estimation thus depends on the accuracy of the transfer function. We have used Finite Element simulations to calculate an in-ear headphone in twenty ear canal geometries of ten different people and compared the results with measurements and simulation of the same headphone in a mannequin outfitted with ear canal simulators. The results show that using the mannequin’s transfer function to predict personalized pressure responses at the ear drum will result in error of up to 7.8 dB below 5 kHz and even greater above 5 kHz. Two simulation studies with different targets at the ear drum showcase the need for better estimates of the transfer function from in-device microphone to eardrum when attempting to control the pressure response at the eardrum.
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