Temporal-Envelope Reconstruction for Hearing-Impaired Listeners

Abstract

Recent studies suggest that normal-hearing listeners maintain robust speech intelligibility despite severe degradations of amplitude-modulation (AM) cues, by using temporal-envelope information recovered from broadband frequency-modulation (FM) speech cues at the output of cochlear filters. This study aimed to assess whether cochlear damage affects this capacity to reconstruct temporal-envelope information from FM. This was achieved by measuring the ability of 40 normalhearing listeners and 41 listeners with mild-to-moderate hearing loss to identify syllables processed to degrade AM cues while leaving FM cues intact within three broad frequency bands spanning the range 65-3,645 Hz. Stimuli were presented at 65 dB SPL for both normalhearing listeners and hearing-impaired listeners. They were presented as such or amplified using a modified half-gain rule for hearing-impaired listeners. Hearingimpaired listeners showed significantly poorer identification scores than normal-hearing listeners at both presentation levels. However, the deficit shown by hearing-impaired listeners for amplified stimuli was relatively modest. Overall, hearing-impaired data and the results of a simulation study were consistent with a poorer-than-normal ability to reconstruct temporalenvelope information resulting from a broadening of cochlear filters by a factor ranging from 2 to 4. These results suggest that mild-to-moderate cochlear hearing loss has only a modest detrimental effect on peripheral, temporal-envelope reconstruction mechanisms.

Consonant identification in noise using Hilbert-transform temporal fine-structure speech and recovered-envelope speech for listeners with normal and impaired hearing

“…Consistent with other studies (Gilbert and Lorenzi, 2006;Swaminathan, 2010;Lorenzi et al, 2012;Swaminathan et al, 2014;L eger et al, 2015), our results suggest that the reception of TFS speech is based on the use of RENVs for both NH and HI listeners. In the current study, the reception of one-band and four-band TFS speech was compared to speech signals created through the extraction of 40 bands of ENVs from each type of TFS speech.…”

“…One is that ENV recovery from TFS speech was already optimal for the HI listeners and thus the artificial-recovery of the ENVs did not provide any further benefit. Second, it is possible that the RENVs were internally smeared due to the broadened auditory bands associated with cochlear hearing loss and thus led to fewer independent usable ENVs (e.g., Baskent, 2006;Swaminathan and Heinz, 2012;Lorenzi et al, 2012). Third, the RENV cues may have been corrupted by the amplification of noise during the generation of TFS speech (see Apoux et al, 2013).…”

“…The results suggested that RENVs played a role in the reception of TFS speech only when the bandwidths of the channels used to generate TFS speech were sufficiently large (i.e., more than 4 times the normal auditory critical bandwidth). Lorenzi et al (2012) recovered envelopes from TFS speech that had been generated within three broad frequency bands and examined the effect of the width of the analysis filters used for ENV extraction. Consonant-identification performance for NH listeners with the RENV signals was somewhat lower than that obtained with the original TFS speech, but was substantially above chance on all conditions and showed improvements with training.…”

Consonant identification using temporal fine structure and recovered envelope cues

“…In a modeling study, Heinz and Swaminathan (2009) simulated the broadening of auditory filters that typically occurs with hearing loss and showed that such broadening resulted in a reduction in the degree to which ENV cues can be recovered from TFS speech. Such broadening of peripheral auditory filters could have an effect on the envelope reconstruction from TFS speech (e.g., Heinz and Swaminathan, 2009;Lorenzi et al, 2012). Thus, it was expected that performance would decrease with a reduction in the number of RENV bands.…”

Use of Amplitude Modulation Cues Recovered from Frequency Modulation for Cochlear Implant Users When Original Speech Cues Are Severely Degraded

“…For example, if the speech processor is mapped with an eight-channel continuous interleaved sampling (CIS) strategy, the bandwidth of the digital filters is approximately three times wider than the bandwidth of the normal auditory filters. Consistent with this prediction, Lorenzi et al (2012) showed that the broadening of cochlear filters typically associated with sensorineural hearing loss has a detrimental effect on the ability to use the AM speech cues recovered from the broadband FM speech cues, when cochlear filters are broadened by a factor greater than two.…”