Robust single- and multi-loudspeaker least-squares-based equalization for hearing devices

• Published in: EURASIP journal on audio, speech, and music processing Vol. 2022; no. 1; pp. 1 - 14
• Main Authors: Schepker, Henning, Denk, Florian, Kollmeier, Birger, Doclo, Simon
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 11-06-2022; Springer Nature B.V; SpringerOpen
• Subjects: Acoustic transparency; Acoustics; Ear; Empirical Research; Engineering; Engineering Acoustics; Equalization; Filter design (mathematics); Group delay; Hearing; Hearing aids; Hearing device; Hearing protection; Least squares; Loudspeakers; Mathematics in Music; Multi-loudspeaker; Regularization; Robustness; Signal processing; Signal,Image and Speech Processing; Sound; Sound filters; Sound pressure equalization; Transfer functions; Sound pressure equalization; Multi-loudspeaker; Acoustic transparency; Hearing device
• ISSN: 1687-4722; 1687-4714; 1687-4722
• DOI: 10.1186/s13636-022-00247-6

To improve the sound quality of hearing devices, equalization filters can be used to achieve 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 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. Depending on the processing delay of the hearing device, comb-filtering artifacts can occur due to this superposition, which may degrade the perceived sound quality. In this paper, we propose a unified least-squares-based procedure to design single- and multi-loudspeaker equalization filters for hearing devices aimed at achieving acoustic transparency. To account for non-minimum phase components, we utilize a so-called group delay compensation. To reduce comb-filtering artifacts, we propose to use a frequency-dependent regularization. Experimental results using measured acoustic transfer functions from a multi-loudspeaker earpiece show that the proposed equalization filter design procedure results in robust acoustic transparency and reduces the impact of comb-filtering artifacts. A comparison between single- and multi-loudspeaker equalization shows that for both cases a robust equalization performance can be achieved for different desired open ear transfer functions.