Energetic and Informational Components of Speech-on-Speech Masking in Binaural Speech Intelligibility and Perceived Listening Effort

Abstract

Speech perception in complex sound fields can greatly benefit from different unmasking cues to segregate the target from interfering voices. This study investigated the role of three unmasking cues (spatial separation, gender differences, and masker time reversal) on speech intelligibility and perceived listening effort in normal-hearing listeners. Speech intelligibility and categorically scaled listening effort were measured for a female target talker masked by two competing talkers with no unmasking cues or one to three unmasking cues. In addition to natural stimuli, all measurements were also conducted with glimpsed speech-which was created by removing the time-frequency tiles of the speech mixture in which the maskers dominated the mixture-to estimate the relative amounts of informational and energetic masking as well as the effort associated with source segregation. The results showed that all unmasking cues as well as glimpsing improved intelligibility and reduced listening effort and that providing more than one cue was beneficial in overcoming informational masking. The reduction in listening effort due to glimpsing corresponded to increases in signal-to-noise ratio of 8 to 18 dB, indicating that a significant amount of listening effort was devoted to segregating the target from the maskers. Furthermore, the benefit in listening effort for all unmasking cues extended well into the range of positive signal-to-noise ratios at which speech intelligibility was at ceiling, suggesting that listening effort is a useful tool for evaluating speech-on-speech masking conditions at typical conversational levels.

Effects of Acquired Aphasia on the Recognition of Speech Under Energetic and Informational Masking Conditions

“…Calculating this difference in thresholds is equivalent, in theory, to subtracting performance on an EM-only condition from performance on an EM-plus-IM condition, leaving only the effects of IM. Additional masking is a particularly meaningful metric because it compares each participant to themselves, thereby controlling for any potential influence of individual differences in performance which may be quite large in IM-dominated speech recognition tasks (cf., Clayton et al, 2016;Kidd & Colburn, 2017;Swaminathan et al, 2015) or to factors that may affect the ability to hear and use glimpses of masked speech (cf., Kidd et al, 2019). The higher levels of additional masking, in conjunction with equivalent group mean thresholds for the glimpsed speech and noise masking conditions, is consistent with the conclusion that PWA are especially adversely affected by competing talkers in "cocktail party" listening situations.…”

“…Our interpretation of the results from the speech masking condition, in which masker sentences were highly similar to and confusable with target sentences, is that this condition produced high levels of IM while causing much lower levels of EM. This conclusion is based on the TMRs at threshold obtained in that condition relative to the thresholds in the glimpsed and noise masking conditions (cf., Kidd et al, 2019;Rennies et al, 2019). These results showed that thresholds in this condition were higher (worse) for PWA than for HC, suggesting that PWA speech processing abilities break down more than those of HC as levels of competing speech are increased, which in turn suggests that PWA are more susceptible to the effects of IM than are HC.…”

“…Their findings suggested that, indeed, release from masking in all speech masker conditions was due primarily to decreased IM. A follow-up study examining EM versus IM in listeners with HL found that, while listeners with HL were more susceptible than normal-hearing listeners to both EM and IM, manipulation of the masker conditions listed earlier provided less benefit to listeners with HL (Kidd et al, 2019). Interestingly, when ITFS processing was applied, listeners with HL obtained smaller improvements in performance than normal-hearing listeners, a result that they speculated could be due to reduced audibility of the remaining glimpses in the ITFS-processed signal or to a reduction in the ability to form coherent streams of speech from the degraded representations of the processed stimuli.…”

“…The specific LC selected may influence the degree to which this second assumption is satisfied: For example, although an LC of 0 dB is often used, the LC may be set at any level, and this value could affect the estimates of EM and IM (cf., Brungart et al, 2006). Despite these caveats, however, ITFS is considered to be the best approach currently available for obtaining a reasonable estimate of IM in a speech-on-speech masking task for a wide range of target-masker combinations (e.g., Rennies et al, 2019).…”

“…The four words in a given category were selected for their phonemic distinguishability from one another; additionally, the four objects were also selected for their ease of imageability and their roughly equal semantic distance from one another. Each word was produced individually with neutral inflection and subsequently concatenated into sentences following the procedures described by Kidd et al (2008) and used in several other studies employing matrix-based closedset speech identification testing (e.g., Best et al, 2013;Kidd et al, 2014Kidd et al, , 2016Kidd et al, , 2019.…”