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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.<\/jats:p>","DOI":"10.1186\/s13636-022-00247-6","type":"journal-article","created":{"date-parts":[[2022,6,11]],"date-time":"2022-06-11T13:05:13Z","timestamp":1654952713000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Robust single- and multi-loudspeaker least-squares-based equalization for hearing devices"],"prefix":"10.1186","volume":"2022","author":[{"given":"Henning","family":"Schepker","sequence":"first","affiliation":[]},{"given":"Florian","family":"Denk","sequence":"additional","affiliation":[]},{"given":"Birger","family":"Kollmeier","sequence":"additional","affiliation":[]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3392-2381","authenticated-orcid":false,"given":"Simon","family":"Doclo","sequence":"additional","affiliation":[]}],"member":"297","published-online":{"date-parts":[[2022,6,11]]},"reference":[{"issue":"4","key":"247_CR1","first-page":"32","volume":"11","author":"M. 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