Individualized prediction of the sound pressure at the eardrum for an earpiece with integrated receivers and microphones.

Steffen Vogl,Matthias Blau

doi:10.1121/1.5089219

Abstract

Future hearing systems and hearables will likely contain microphones and receivers in the ear canal. In order to predict the sound pressure at the eardrum in such a scenario, a one-dimensional electroacoustic model of a prototype open earpiece with integrated receivers and integrated microphones was developed. The model parameters were obtained in a training setup with well-defined loads at both sides of the earpiece. Subsequently, the prototype earpiece was put on individual subjects, and the model was then used to determine the acoustic impedance of the ear canal, which in turn was used to derive models of the individual ear canal and eardrum, by minimizing five types of cost functions and various parameters. Model predictions of the sound pressure at the individual eardrum were subsequently compared to probe-tube measurements in 12 human subjects. An analysis of the resulting errors led to identifying the best combination of cost function and associated parameters. This best combination resulted in an agreement between measurement and prediction of less than ±3 dB and ±20° up to 3 kHz and less than ±5 dB and ±30° up to 6-8 kHz, performing significantly better than both average transfer models and existing individualized predictions.

Highlights

Open hearing aids that do not seal the ear canal are very popular, in particular, because they avoid the occlusion effect, i.e., the unwanted amplification of lowfrequency components of one’s own voice
We address the scenario where the hearing system is inserted, i.e., the problem of individually predicting the sound pressure created by the receivers at the eardrum, by using electroacoustic models of the hearing system and individual ear
In an attempt toward a more robust approach that could be used for hearing systems such as the one described in Denk et al (2017b), we propose to use an electroacoustic model (a) capable of correctly reproducing the individual interaction between source and ear canal, and (b) comprising individual ear canal and drum models

Summary

Introduction

Open hearing aids that do not seal the ear canal are very popular, in particular, because they avoid the occlusion effect, i.e., the unwanted amplification of lowfrequency components of one’s own voice. One could use electroacoustic models to better understand the acoustic transfer properties within the individual ear, both in the original open-ear case and in the case with the hearing system inserted. This could eventually be used to derive control strategies to achieve drum pressure equalization as well as active feedback, noise, and occlusion control. The transfer functions of the sound pressure at the eardrum relative to either the electrical voltage applied to a receiver or the sound pressure measured by the innermost microphone in the vent must be predicted individually

Results

Discussion

Conclusion