The subjective evaluation of the expansion time constant in single-channel wide dynamic range compression hearing instruments

Abstract

The present study investigated the subjective evaluation of expansion time constants in single-channel wide dynamic range compression (WDRC) hearing instruments. Thirty participants utilized binaural WDRC hearing instruments for a two-week trial. Subjective evaluations were conducted by having each participant rate their satisfaction with the expansion time constant on a daily basis and by having each participant indicate their preferred expansion time constant following the completion of the two-week trial. Each change in expansion time constant significantly affected listener satisfaction; however, all time constants resulted in satisfactory performance. Of the users expressing a preference, 75% preferred fast-acting over slow-acting expansion. These findings suggest that dynamic expansion parameters play an important role in determining the effectiveness of the feature for a given listener.

The Objective and Subjective Evaluation of Low-Frequency Expansion in Wide Dynamic Range Compression Hearing Instruments

“…Differences in listener satisfaction ratings in low-level environments observed between the present and previous research could be attributed to the methodological differences used between investigations. In previous research, participants evaluated each expansion condition in their own homes instead of in the laboratory in order to examine the effects of expansion in the real-world settings for which expansion was designed (Plyler et al, 2005a;Plyler et al, 2007;Plyler et al, 2006). Participants were instructed to conduct their everyday environment evaluations while paying close attention to soft sounds such as having a quiet conversation with one other person, listening to leaves rustling, watching television at a low volume, etc.…”

“…Participants were instructed to conduct their everyday environment evaluations while paying close attention to soft sounds such as having a quiet conversation with one other person, listening to leaves rustling, watching television at a low volume, etc. (Plyler et al, 2005a;Plyler et al, 2007;Plyler et al, 2006). Consequently, it is possible some participants did not listen to speech when evaluating expansion in their everyday environment while others rarely listened to speech at such low levels.…”

“…In either case, speech-recognition deficits from expansion activation would have gone unnoticed and would not impact the subjective results. Conversely, it is also possible that the noise-reduction benefits produced by expansion outweighed the speech-recognition deficits produced when listening in a low-level environment given the fact most listeners preferred the use of expansion (Plyler et al, 2005a;Plyler et al, 2007;Plyler et al, 2006).…”

“…In previous expansion studies, subjective evaluations were conducted in the participants' own homes instead of in the laboratory to examine expansion in the real-world settings for which it was designed (Plyler et al, 2005a;Plyler et al, 2006;Plyler et al, 2007). In the present study, subjective evaluations were conducted in laboratory to determine if laboratory findings agree with those obtained in more real-world listening environments.…”

“…Expansion was designed to provide reduced gain for signals below the compression kneepoint rather than maximum gain in order to reduce the audibility of these unwanted, low-level signals (Venema, 1998;Ghent et al, 2000;Kuk, 2002). Recent research has demonstrated that single-channel expansion improves subjective performance for WDRC hearing instrument users (Plyler et al, 2005a;Plyler et al, 2006) despite degrading the recognition of low-level speech (Plyler et al, 2005a, Plyler et al, 2005b.…”