Ellen Lundorff1,2,3, Rasmus Skipper4, Tobias Neher1,2, Georg Stiefenhofer3
Institute of Clinical Research, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark
2Research Unit for ORL – Head & Neck Surgery and Audiology, Odense University Hospital, Odense, Denmark; University of Southern Denmark, Odense, Denmark
3Scientific Audiology, WS Audiology A/S, Lynge, Denmark
4Dept. of Audiology, Odense University Hospital, Odense, Denmark

Sound quality is a critical component for hearing-aid satisfaction and uptake (Kochkin, 2010). A key factor influencing sound quality is the inherent processing delay of hearing aids, which causes audible effects when the processed sound mixes with the direct (un-delayed) sound that enters the ear canal through a dome or vent of an earmold. Depending on the size of the delay, the resulting effect relates to changes in sound timbre, perception of echoes, and altered spatial qualities. Modern hearing aids have delays of approximately 5-10 ms, with 10 ms being the current ‘gold standard’ for what is deemed tolerable (Stone et al., 2008). It is still unclear, however, how short the delay needs to be for ensuring optimal sound quality for the user. This question is of interest because the latest advances in signal processing allow for much shorter delays to be realized in hearing devices. The current study therefore explored the effects of six different hearing-aid delays ranging from 0.2 to 10 ms on perceived sound quality with the help of a realistic hearing-aid simulator. Three types of stimuli and two gain settings were tested. The participants were 10 normal-hearing subjects and 20 subjects with mild-to-moderate sensorineural hearing losses. From the results, it is expected that hearing-aid delay will be inversely related to perceived sound quality, with delays <1 ms resulting in best outcome overall. Hearing loss severity, stimulus type and gain setting are expected to affect this relationship.