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

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.