Role of Binaural Temporal Fine Structure and Envelope Cues in Cocktail-Party Listening

Abstract

While conversing in a crowded social setting, a listener is often required to follow a target speech signal amid multiple competing speech signals (the so-called "cocktail party" problem). In such situations, separation of the target speech signal in azimuth from the interfering masker signals can lead to an improvement in target intelligibility, an effect known as spatial release from masking (SRM). This study assessed the contributions of two stimulus properties that vary with separation of sound sources, binaural envelope (ENV) and temporal fine structure (TFS), to SRM in normal-hearing (NH) human listeners. Target speech was presented from the front and speech maskers were either colocated with or symmetrically separated from the target in azimuth. The target and maskers were presented either as natural speech or as "noise-vocoded" speech in which the intelligibility was conveyed only by the speech ENVs from several frequency bands; the speech TFS within each band was replaced with noise carriers. The experiments were designed to preserve the spatial cues in the speech ENVs while retaining/eliminating them from the TFS. This was achieved by using the same/different noise carriers in the two ears. A phenomenological auditory-nerve model was used to verify that the interaural correlations in TFS differed across conditions, whereas the ENVs retained a high degree of correlation, as intended. Overall, the results from this study revealed that binaural TFS cues, especially for frequency regions below 1500 Hz, are critical for achieving SRM in NH listeners. Potential implications for studying SRM in hearing-impaired listeners are discussed.

The effect of tone-vocoding on spatial release from masking for old, hearing-impaired listeners

“…They retained or removed ITD-based cues of spatial separation in the TFS by vocoding with either the same or uncorrelated noises at each ear, respectively. Swaminathan et al (2016) found that correlated-noise vocoding produced similar SRTs and SRM to non-vocoded stimuli, but vocoding with interaurally uncorrelated noises produced poorer SRTs and SRM. The effect of noise vocoding on SRM was predominantly driven by the interaural correlation of the noise carriers below 1.5 kHz.…”

“…This extra elevation suggests that binaural TFS cues, even carried by TVC signals, can help speech intelligibility. More recent evidence suggests a greater role of binaural TFS cues and a smaller role of the original speech TFS: Swaminathan et al (2016) studied the effect on SRM of noise vocoding before convolving speech with HRIRs. They retained or removed ITD-based cues of spatial separation in the TFS by vocoding with either the same or uncorrelated noises at each ear, respectively.…”

Broad binaural fusion impairs segregation of speech based on voice pitch differences in a ‘cocktail party’ environment

“…One likely reason for the reduced spatial benefit for HI users is that they have limited access to sound localization cues on the horizontal plane such as interaural time difference (ITD) and interaural level difference (ILD) cues. Previous studies have shown that ITD sensitivity is particularly important for localization performance and speech perception in noise (Gifford et al, 2013;Swaminathan et al, 2016;Ellinger et al, 2017). Phase-locking and ITD sensitivity can both be impaired with hearing loss (Henry and Heinz, 2013;Dai et al, 2018).…”

Electrophysiological and Behavioral Evidence of Reduced Binaural Temporal Processing in the Aging and Hearing Impaired Human Auditory System

“…Adequate processing of both envelope and TFS information is indispensable for speech understanding ( Swaminathan & Heinz, 2012 ; Zeng et al., 2005 ). Moreover, binaural TFS processing underlies spatial release from masking, that is, a binaural advantage that results in improved speech understanding when a speech target is spatially separated from interfering sound streams ( Swaminathan et al., 2016 ). This study was designed to gain more insight in age- and HI-related changes in binaural TFS processing throughout adult life.…”