Niels Overby1, Torsten Dau1, Tobias May1
1Hearing Systems Section, Department of Health Technology, Technical University of Denmark, Kgs. Lyngby, Denmark

Dynamic range compression aims to restore audibility for hearing-impaired listeners and is one of the most essential building blocks in modern hearing aids. However, the choice of suitable compression parameters, such as the time constants associated with the level estimation stage, depends on the acoustic conditions, and the perceptual benefit of different parameter configurations is still controversial. Listening tests can provide an accurate assessment of the perceptual effects of compression in a limited set of acoustic conditions, but they are time-consuming and can therefore not be used to optimize the various compression parameters across experimental conditions. While several studies have attempted to link the perceptual outcomes of dynamic range compression to a set of objective metrics, there is no agreement on how to objectively quantify the effects of compression. In the current study, a data-driven distance metric was developed based on objective metrics to analyze different compression systems. This analysis included slow-acting, fast-acting, and ‘scene-aware’ compression that adaptively switched between fast- and slow-acting compression depending on the target source activity. In addition, a reference system termed ‘source-independent compression’ was considered that had access to the individual speech and noise signals. A comprehensive list of objective metrics was considered to evaluate the effect of the different compression systems in a wide variety of acoustic conditions, including both interfering noise and room reverberation. Sparse principal component analysis (PCA) was then applied to derive a compact set of interpretable features that explained the effects of compression as linear combinations of sparsely selected objective metrics. The Euclidean distance, within the reduced dimensionality representation, was used to compare the similarity between the compression systems. This newly developed distance metric allows a systematic analysis and optimization of the parameters of dynamic range compression systems by minimizing the Euclidean distance with respect to the source-independent compression system.