The preferred response slopes and two-channel compression ratios in twenty listening conditions by hearing-impaired and normal-hearing listeners and their relationship to the acoustic input

Abstract

This paper presents the results from two experiments in which normal-hearing and hearing-impaired listeners used an adaptive procedure to select their preferred frequency response slope and two-channel compression ratios in twenty listening conditions. Whereas the preferred response slope mostly depended on the difference in SNR between frequency bands, the preferred output levels in two channels depended highly on the intensity level entering each band. In both cases, subjects preferred less gain in frequency bands where noise was more intrusive and they preferred less gain for listening comfort than for speech understanding. The preferred response slope also depended on the slope of the audiogram. Relative to the prescribed NAL-RP response, the preferred gain variations improved the broadband SNR and hence listening comfort, but not the estimated speech intelligibility index. Overall, the findings confirm the approach used in many commercial products of applying wide dynamic range compression in multiple bands with additional gain reductions in bands where the noise is estimated to be dominant.

Client-Based Adjustments of Hearing Aid Gain: The Effect of Different Control Configurations

“…4B). This is in agreement with findings of Keidser et al (2005). Although there were no significant effects of controller on the selected slope (p ϭ 0.67), there was a moderately significant effect of controller on the selected overall gain (p ϭ 0.01).…”

“…Another reason for the increase in hearing aid fitting complexity is that modern hearing aids allow activation of different processing strategies for different acoustical environments, as it is widely accepted that hearing aid users prefer different responses for different listening situations (Keidser, 1995;Keidser, et al, 2005). Unlike the gain-frequency response of a hearing aid, which is traditionally determined by an individual's audiometric data, it has been suggested that modern hearing aid features should be fitted according to the characteristics of the acoustic environment (Kiessling, 2001).…”

NAL-NL2 Empirical Adjustments

“…The smaller the dynamic range of hearing is at a given frequency, the higher a CR would be needed to make all speech sounds audible. However, applying compression to the rapidly fluctuating speech signal causes some level of distortion to both the spectral and temporal cues (e.g., Bustamante & Braida, 1987;Moore, 1990;Plomp, 1988), and several studies suggest that for people with mild or moderate hearing loss such distortions have a deleterious effect on speech discrimination, or diminish ratings of sound quality and preference, when using CRs much greater than 3:1 in conjunction with fast time constants and multiple channels (Keidser et al, 2005a;Neuman, Bakke, Mackersie, Hellman, & Levitt, 1998;Plomp, 1994;Verschuure, Prinsen, Dreschler, 1994). Therefore, a compromise between audibility and acceptable sound quality and optimum speech understanding seems inevitable.…”

Evidence on Self-Fitting Hearing Aids

“…Various prescription methods result in prescription targets that differ from individually preferred gain by up to 10 dB or more, particularly at the high frequencies Keidser et al, 2005;Keidser, O'Brien, Carter, McLelland, & Yeend, 2008;Mueller, 2005;Polonenko, Scollie, & Moodie, 2010;Smeds et al, 2006;Zakis, Dillon, & McDermott, 2007). Other studies have reported that mean preferred overall gain is about 3 to 4 dB less than the prescriptive targets Horwitz & Turner, 1997;Humes, Wilson, Barlow, & Garner, 2002;Keidser, O'Brien, et al, 2008;Marriage et al, 2004;Mueller & Bentler, 2005;Polonenko et al, 2010;Zakis et al, 2007).…”

“…In a laboratory experiment, Keidser et al (2005) found that less gain is preferred in frequency bands where noise is more annoying and the preferred frequency response slopes depend on the slope of the audiogram. Convery et al (2005), Keidser, Dillon, et al (2008) and Smeds et al (2006) also found that the preferred gain-frequency response varied with listening conditions.…”