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

Abstract

The effects of low-frequency expansion on the objective and subjective evaluation of four channel in-the-ear hearing instruments was investigated. Three expansion settings were programmed in each device: expansion off, expansion restricted to channel one, and expansion restricted to channels one and two. Objective evaluations were conducted in quiet (Connected Speech Test) and in noise (Hearing in Noise Test) with speech levels fixed at 40 dB SPL. Subjectively, each participant rated expansion satisfaction in quiet and listening to low-level speech in a sound-treated room then indicated the expansion condition preferred overall. Listeners performed significantly better in quiet and in noise for the Off and Channel 1 conditions than the Channels 1 and 2 condition; however, performance was similar between the Off and Channel 1 conditions. Expansion effects on listener satisfaction ratings depended on the listening environment. Overall, listeners preferred expansion in Channel 1 to expansion in Channels 1 and 2; however, preference was not significantly different between the Channel 1 and Off conditions. Results indicate restricting expansion to 1000 Hz overcomes speech-recognition deficits observed with expansion active across a broader spectrum without significantly reducing subjective benefit or preference.

Effects of Expansion on Consonant Recognition and Consonant Audibility

“…T he results confirmed the first hypothesis: CV recognition decreased significantly for the high expansion kneepoint condition. These findings are consistent with previous studies that found reduced speech recognition with high kneepoints in all or some of the frequency channels (Walker et al, 1984;Plyler et al, 2005aPlyler et al, , 2005bLowery and Plyler, 2007;Plyler et al, 2007;Zakis and Wise, 2007). This was the first study to have used low-level kneepoints in all frequency channels.…”

“…Methodology differences could account for the discrepancies. The studies that found a preference for expansion had subjects rate expansion while using undesirable stimuli, such as low-level noise situations (Plyler et al, 2005a;Plyler et al, 2006;Lowery and Plyler, 2007;Plyler et al, 2007). The studies that found a preference for linear amplification used desirable stimuli, such as speech or music (Walker et al, 1984;van Buuren et al, 1999;Lowery and Plyler, 2007).…”

“…Clearly an implementation of expansion that does not significantly degrade speech recognition needs to be developed. One possible way to reduce the effect of expansion is to restrict the use of expansion to lowfrequency channels, as argued by Lowery and Plyler (2007). Lowery and Plyler found that restricting expansion to below 1000 Hz did not significantly affect sentence recognition.…”

Tobacco Smoke Exposure during Childhood: Effect on Cochlear Physiology

“…Studies involving smoking and nonsmoking adults have demonstrated that the levels of transient evoked otoacoustic emissions (TEOAEs) were significantly lower in the smokers [17,18,19,20,21,22]. Given the emerging evidence of a relationship between primary tobacco smoking and hearing loss it is reasonable to postulate that a similar association exists between passive smoking and hearing loss.…”