Multi-loudspeaker equalization for acoustic transparency in a custom hearing device

To improve the sound quality of hearing devices, equalization algorithms can be used that aim at achieving acoustic transparency, i.e., listening with the device in the ear is perceptually similar to the open ear. The equalization filter needs to ensure that the superposition of the processed and equalized signal played by the device and the signal leaking through the device into the ear canal matches a processed version of the signal reaching the eardrum of the open ear. Since equalization using a single loudspeaker typically does not allow for perfect equalization, in this paper we propose to use a multi-loudspeaker equalization filter to achieve acoustic transparency in a custom multiloudspeaker hearing device. The equalization filter is computed by minimizing a regularized least-squares optimization problem. Experimental results using measured acoustic transfer functions show that the proposed multi-loudspeaker equalization filter is able to provide the desired signal at the eardrum for different gains and delays of the hearing device.