Intelligibility of whispered speech in stationary and modulated noise maskers

Abstract

This study investigated the role of natural periodic temporal fine structure in helping listeners take advantage of temporal valleys in amplitude-modulated masking noise when listening to speech. Young normal-hearing participants listened to natural, whispered, and/or vocoded nonsense sentences in a variety of masking conditions. Whispering alters normal waveform temporal fine structure dramatically but, unlike vocoding, does not degrade spectral details created by vocal tract resonances. The improvement in intelligibility, or masking release, due to introducing 16-Hz square-wave amplitude modulations in an otherwise steady speech-spectrum noise was reduced substantially with vocoded sentences relative to natural speech, but was not reduced for whispered sentences. In contrast to natural speech, masking release for whispered sentences was observed even at positive signal-to-noise ratios. Whispered speech has a different short-term amplitude distribution relative to natural speech, and this appeared to explain the robust masking release for whispered speech at high signal-to-noise ratios. Recognition of whispered speech was not disproportionately affected by unpredictable modulations created by a speech-envelope modulated noise masker. Overall, the presence or absence of periodic temporal fine structure did not have a major influence on the degree of benefit obtained from imposing temporal fluctuations on a noise masker.

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

“…Based on their results, these authors concluded that the MR observed for TFS speech may arise from the use of RENV rather than TFS. This observation agrees with recent studies that question the role of TFS cues for aiding in speech perception in the presence of fluctuating interference (Oxenham and Simonson, 2009;Freyman et al, 2012).…”

“…However, the importance of TFS cues for "listening in the gaps" has been called into question by several studies exploring this hypothesis (Oxenham and Simonson, 2009;Freyman et al, 2012). For example, Oxenham and Simonson (2009) did not find a greater MR for low-pass filtered speech (which would contain TFS cues) compared to high-pass filtered speech (where TFS cues for resolved harmonics would be absent).…”

“…For example, Oxenham and Simonson (2009) did not find a greater MR for low-pass filtered speech (which would contain TFS cues) compared to high-pass filtered speech (where TFS cues for resolved harmonics would be absent). In studies using whispered speech (which removes natural TFS cues but does not alter the spectral details of the vocal-tract resonance), Freyman et al (2012) observed a substantial MR that was constant across a wide range of SNR, as well as a small MR for a vocoded signal created from the whispered speech.…”

Development of a method for determining binaural sensitivity to temporal fine structure

“…It has been proposed that TFS cues may be important for the perceptual separation of target speech from interfering sounds (Hopkins and Moore 2011;Moore 2014) and may underlie the ability to take advantage of the energetic minima in fluctuating background sounds, so-called dip listening (Lorenzi and Moore 2008). The latter proposal is however contradicted by studies showing that dip-listening performance for speech in noise is similar for speech containing strong or intact TFS cues and speech containing weak or altered TFS cues (Oxenham and Simonson 2009;Freyman, Griffin, and Oxenham 2012). In addition, Füllgrabe, Moore, and Stone (2015) found no significant association between TFS sensitivity and a measure of dip listening for young and older normal-hearing (NH) listeners.…”

Level variations in speech: Effect on masking release in hearing-impaired listeners

“…Hopkins and Moore (2009), for example, observed an increase in MR with an increase in the number of spectral channels in which TFS cues were present. However, other studies have found no direct link between TFS cues and MR (e.g., Oxenham and Simonson, 2009;Bernstein and Brungart, 2011;Freyman et al, 2012). Recently, it has been suggested that MR arises in NH listeners due to a release from the random modulations present in nominally steady noise (e.g., Stone et al, 2012).…”