A Glimpsing Account of the Role of Temporal Fine Structure Information in Speech Recognition

Abstract

Many behavioral studies have reported a significant decrease in intelligibility when the temporal fine structure (TFS) of a sound mixture is replaced with noise or tones (i.e., vocoder processing). This finding has led to the conclusion that TFS information is critical for speech recognition in noise. How the normal -auditory system takes advantage of the original TFS, however, remains unclear. Three -experiments on the role of TFS in noise are described. All three experiments measured speech recognition in various backgrounds while manipulating the envelope, TFS, or both. One experiment tested the hypothesis that vocoder processing may artificially increase the apparent importance of TFS cues. Another experiment evaluated the relative contribution of the target and masker TFS by disturbing only the TFS of the target or that of the masker. Finally, a last experiment evaluated the -relative contribution of envelope and TFS information. In contrast to previous -studies, however, the original envelope and TFS were both preserved - to some extent - in all conditions. Overall, the experiments indicate a limited influence of TFS and suggest that little speech information is extracted from the TFS. Concomitantly, these experiments confirm that most speech information is carried by the temporal envelope in real-world conditions. When interpreted within the framework of the glimpsing model, the results of these experiments suggest that TFS is primarily used as a grouping cue to select the time-frequency regions -corresponding to the target speech signal.

Speech recognition interference by the temporal and spectral properties of a single competing talker

“…Combined with the above evidence, this suggests that while TFS may enhance source segregation, it still appears to contribute to linguistic interference of segregated signals. This finding is significant regarding recent discussions related to the role of TFS for source segregation and linguistic processing (Apoux and Healy, 2013;Fogerty and Entwistle, 2015). …”

“…Processing selectively preserved amplitude modulations (ENV) and degraded frequency modulations conveyed by the temporal fine structure (TFS). This method has the advantage of limiting cues provided by the acoustic TFS while avoiding confounds of vocoder processing that use the same carrier for both target and competing stimuli (Apoux and Healy, 2013). First, the speech signal was combined with noise matching the same power spectrum of the target speech at 11 dB signal-to-noise ratio (SNR).…”

“…Indeed, they have even described the random amplitude fluctuations intrinsic to "steady-state" noise, traditionally defined as an energetic masker, as also, or perhaps primarily, imposing modulation-based interference. Considerable evidence now suggests that primary information regarding the speech message is conveyed by the amplitude modulations of speech (e.g., Shannon et al, 1995;Fogerty, 2011;Apoux and Healy, 2013). The importance of amplitude modulations (i.e., temporal envelope) for speech recognition therefore warrants a direct investigation to examine the likely potential for modulation interference from a competing talker.…”

Effects of steep high-frequency hearing loss on speech recognition using temporal fine structure in low-frequency region

“…Unless otherwise indicated, we will regard "E" and "TFS" as the acoustic E and acoustic TFS specifically in this paper. Several studies have shown that TFS information is important for speech perception, especially in a noisy background (Hopkins and Moore, 2009;Hopkins et al, 2008) although a recent study has questioned this (Apoux and Healy, 2013). In view of the important role of TFS in speech recognition and the speech perception problems in SNHL participants in noisy conditions, it has been assumed that TFS perception problems may exist in SNHL participants (Gnansia et al, 2009;Moore, 2008).…”

Evidence for independent time-unit processing of speech using noise promoting or suppressing masking release

“…The relative independence with which various timefrequency (T-F) units of speech may be processed is relevant to the glimpsing model of speech perception in noise (Cooke, 2006;Apoux and Healy, 2013) and to binarymasking techniques used to separate speech from noise (e.g., Wang, 2005). In the glimpsing model, the auditory system bases the speech percept on T-F units containing relatively clean speech and essentially disregards T-F units dominated by noise.…”