Influence of suppression on restoration of spectral loudness summation in listeners with hearing loss

Abstract

Loudness depends on both the intensity and spectrum of a sound. Listeners with normal hearing perceive a broadband sound as being louder than an equal-level narrowband sound because loudness grows nonlinearly with level and is then summed across frequency bands. This difference in loudness as a function of bandwidth is reduced in listeners with sensorineural hearing loss (SNHL). Suppression, the reduction in the cochlear response to one sound by the simultaneous presentation of another sound, is also reduced in listeners with SNHL. Hearing-aid gain that is based on loudness measurements with pure tones may fail to restore normal loudness growth for broadband sounds. This study investigated whether hearing-aid amplification that mimics suppression can improve loudness summation for listeners with SNHL. Estimates of loudness summation were obtained using measurements of categorical loudness scaling (CLS). Stimuli were bandpass-filtered noises centered at 2 kHz with bandwidths in the range of 0.1-6.4 kHz. Gain was selected to restore normal loudness based on CLS measurements with pure tones. Gain that accounts for both compression and suppression resulted in better restoration of loudness summation, compared to compression alone. However, restoration was imperfect, suggesting that additional refinements to the signal processing and gain-prescription algorithms are needed.

Uni- and bilateral spectral loudness summation and binaural loudness summation with loudness matching and categorical loudness scaling

“…In one of the aided conditions, they also accounted for the effects of suppression, the reduction in the cochlear response to a sound due to the simultaneous presence of other sounds. Rasetshwane et al (2018) found that spectral loudness summation was higher-than-normal for the aided conditions, although the differences between moderate hearing-impaired listeners and normal-hearing listeners decreased when suppression was taken into account. Oetting et al (2016) investigated spectral and binaural loudness summation for 9 normal-hearing listeners and 10 hearingimpaired listeners.…”

“…Spectral loudness summation is investigated generally by varying the bandwidth of a noise or tone complex geometrically centred around a certain frequency, where the centre frequency is usually in the range between 1000 and 3200 Hz (e.g., Zwicker, Flottorp, and Stevens 1957;Verhey and Kollmeier 2002;Anweiler and Verhey 2006;Bonding and Elberling 1980;Rasetshwane et al 2018). As a consequence of varying the centre frequency of the signals in our experiments, the results of the current study cannot be compared directly with other studies on spectral loudness summation.…”

“…Finally, current prescription rules implicitly assume that loudness growth is the same for subjects with the same hearing loss. However, Oetting et al (2016), Van Beurden et al (2018, and Rasetshwane et al (2018) all showed that individual differences in spectral loudness summation were substantial, even for subjects with similar degrees of hearing loss. Large inter-individual differences in the loudness domain have been found earlier in literature on the measurement of the LDL.…”

“…Hearing loss has been shown to decrease spectral loudness summation (e.g. Scharf and Hellman 1966;Florentine and Zwicker 1979;Garnier et al 1999, Rasetshwane et al 2018. As the subjects had more hearing loss in the higher frequencies, this may have decreased loudness for the high-pass filtered pink noise.…”

“…Prescription rules based on this model therefore assume decreased spectral loudness summation. However, some recent studies have shown that spectral loudness summation for individual hearing-impaired listeners can be clearly higher than spectral loudness summation for normal-hearing listeners, after an appropriate compensation of the hearing loss (Oetting et al 2016;Van Beurden et al 2018;Rasetshwane et al 2018). Rasetshwane et al (2018) measured the effect of monaural hearing aid amplification on spectral loudness summation.…”