Masking release for hearing-impaired listeners: The effect of increased audibility through reduction of amplitude variability

Abstract

The masking release (i.e., better speech recognition in fluctuating compared to continuous noise backgrounds) observed for normal-hearing (NH) listeners is generally reduced or absent in hearing-impaired (HI) listeners. One explanation for this lies in the effects of reduced audibility: elevated thresholds may prevent HI listeners from taking advantage of signals available to NH listeners during the dips of temporally fluctuating noise where the interference is relatively weak. This hypothesis was addressed through the development of a signal-processing technique designed to increase the audibility of speech during dips in interrupted noise. This technique acts to (i) compare short-term and long-term estimates of energy, (ii) increase the level of short-term segments whose energy is below the average energy, and (iii) normalize the overall energy of the processed signal to be equivalent to that of the original long-term estimate. Evaluations of this energy-equalizing (EEQ) technique included consonant identification and sentence reception in backgrounds of continuous and regularly interrupted noise. For HI listeners, performance was generally similar for processed and unprocessed signals in continuous noise; however, superior performance for EEQ processing was observed in certain regularly interrupted noise backgrounds.

Signal-to-Noise-Ratio-Aware Dynamic Range Compression in Hearing Aids

“…Moreover, Gatehouse, Naylor, and Elberling ( 2003 , 2006 ) suggested that if the noise is fluctuating with distinct temporal dips, fast-acting compression would provide differential amplification by applying more gain to the low-intensity glimpses of the speech than to the noise peaks, potentially leading to improved intelligibility. This prediction is consistent with recent results from Rhebergen, Maalderink, and Dreschler (2017) and Desloge, Reed, Braida, Perez, and D'Aquila (2017) , who established a link between increased speech audibility and improved speech intelligibility when applying fast-acting compression to speech in the presence of fluctuating background noise. On the contrary, compression can negatively affect the output SNR by reducing the speech level and overamplifying portions of the noise occurring in the speech gaps ( Alexander & Masterson, 2014 ; Hagerman & Olofsson, 2004 ; Naylor & Johannesson, 2009 ; Rhebergen et al., 2017 ; Souza et al., 2006 ).…”

Effects of Slow- and Fast-Acting Compression on Hearing-Impaired Listeners’ Consonant–Vowel Identification in Interrupted Noise

“…It is, however, unclear whether this would generalize to a broader range of interferers and speech stimuli. Recently, Desloge et al. (2017) proposed a system equalizing the short- and long-term energy of the signal, somewhat similar to instantaneous compression.…”

“…The noise was composed of five 100-ms bursts, separated by 100-ms silent gaps (corresponding to a 5-Hz repetition rate). Although rather artificial in nature, this noise envelope had the advantage that the sharp onsets and offsets and relatively long silent gaps emphasized the effects of compression time constants while ensuring that the consonant portion of speech would be affected by nonsimultaneous masking only ( Desloge et al., 2017 ; Wilson et al., 2010 ). White noise (bandlimited between 0 and 22050 Hz) was chosen as a carrier to maximize masking of high-frequency consonants and to reduce potential spectral splatter due to noise onsets and offsets.…”

“…Shorter release times allow more gain to be applied to the low-intensity speech components (e.g., consonants) that follow other, high-intensity components (e.g., vowels) or noise bursts. This increased gain can potentially improve audibility and reduce the amount of forward masking, which in turn might lead to an improved speech recognition performance in HI listeners ( Alexander & Rallapalli, 2017 ; Desloge, Reed, Braida, Perez, & D’Aquila, 2017 ; Desloge, Reed, Braida, Perez, & Delhorne, 2010 ; Edwards, 2002 ; Jenstad & Souza, 2005 ; Souza & Turner, 1998 , 1999 ). On the other hand, with a very short release time, the gain follows the fast fluctuations of the signal, effectively reducing the temporal contrast and altering natural modulations in speech ( Alexander & Rallapalli, 2017 ; Souza & Turner, 1996 , 1998 ; Stone & Moore, 2003 , 2004 , 2007 , 2008 ).…”

Auditory tests for characterizing hearing deficits in listeners with various hearing abilities: The BEAR test battery

“…Audibility (in conditions with fluctuating maskers), frequency selectivity (in conditions with stationary noise), and temporal processing acuity (in conditions with speech interferers), have been identified as important factors affecting speech reception thresholds in noise (e.g. Desloge, Reed, Braida, Perez, & D’Aquila, 2017; Johannesen, Pérez-González, Kalluri, Blanco, & Lopez-Poveda, 2016; Oxenham & Simonson, 2009; Rhebergen, Versfeld, & Dreschler, 2006). Thus, a hearing evaluation that goes beyond pure-tone sensitivity and speech intelligibility in quiet would be expected to provide a more accurate characterization of a listener’s hearing deficits.…”