Glimpsing speech interrupted by speech-modulated noise

Interrupted mosaic speech revisited: Gain and loss in intelligibility by stretchinga)

Our previous investigation on the effect of stretching spectrotemporally degraded and temporally interrupted speech stimuli showed remarkable intelligibility gains [Udea, Takeichi, and Wakamiya (2022). J. Acoust. Soc. Am. 152(2), 970-980]. In this previous study, however, gap durations and temporal resolution were confounded. In the current investigation, we therefore observed the intelligibility of so-called mosaic speech while dissociating the effects of interruption and temporal resolution. The intelligibility of mosaic speech (20 frequency bands and 20 ms segment duration) declined from 95% to 78% and 33% by interrupting it with 20 and 80 ms gaps. Intelligibility improved, however, to 92% and 54% (14% and 21% gains for 20 and 80 ms gaps, respectively) by stretching mosaic segments to fill silent gaps (n = 21). By contrast, the intelligibility was impoverished to a minimum of 9% (7% loss) when stretching stimuli interrupted with 160 ms gaps. Explanations based on auditory grouping, modulation unmasking, or phonemic restoration may account for the intelligibility improvement by stretching, but not for the loss. The probability summation model accounted for "U"-shaped intelligibility curves and the gain and loss of intelligibility, suggesting that perceptual unit length and speech rate may affect the intelligibility of spectrotemporally degraded speech stimuli.

The role of glimpses with different energy in speech-in-noise recognition

Listeners can understand speech in noise by "glimpsing" some of the speech regions less affected by noise. This study investigates the contributions of those spectro-temporal regions, known as glimpses, at different energy levels to speech intelligibility in noise. Two listening experiments were conducted to examine the intelligibility of speech in different glimpse compositions in two types of noise. The results suggest that glimpsed spectro-temporal regions with energy above the mean noise level are the primary cue for speech perception in noise, and that listeners can use less-robust cues until at least 15 dB below the glimpsing threshold.

Access to semantic cues does not lead to perceptual restoration of interrupted speech in cochlear-implant users

Cochlear-implant (CI) users experience less success in understanding speech in noisy, real-world listening environments than normal-hearing (NH) listeners. Perceptual restoration is one method NH listeners use to repair noise-interrupted speech. Whereas previous work has reported that CI users can use perceptual restoration in certain cases, they failed to do so under listening conditions in which NH listeners can successfully restore. Providing increased opportunities to use top-down linguistic knowledge is one possible method to increase perceptual restoration use in CI users. This work tested perceptual restoration abilities in 18 CI users and varied whether a semantic cue (presented visually) was available prior to the target sentence (presented auditorily). Results showed that whereas access to a semantic cue generally improved performance with interrupted speech, CI users failed to perceptually restore speech regardless of the semantic cue availability. The lack of restoration in this population directly contradicts previous work in this field and raises questions of whether restoration is possible in CI users. One reason for speech-in-noise understanding difficulty in CI users could be that they are unable to use tools like restoration to process noise-interrupted speech effectively.

Speech Intelligibility Prediction using Spectro-Temporal Modulation Analysis

Spectro-temporal modulations are believed to mediate the analysis of speech sounds in the human primary auditory cortex. Inspired by humans' robustness in comprehending speech in challenging acoustic environments, we propose an intrusive speech intelligibility prediction (SIP) algorithm, wSTMI, for normal-hearing listeners based on spectro-temporal modulation analysis (STMA) of the clean and degraded speech signals. In the STMA, each of 55 modulation frequency channels contributes an intermediate intelligibility measure. A sparse linear model with parameters optimized using Lasso regression results in combining the intermediate measures of 8 of the most salient channels for SIP. In comparison with a suite of 10 SIP algorithms, wSTMI performs consistently well across 13 datasets, which together cover degradation conditions including modulated noise, noise reduction processing, reverberation, near-end listening enhancement, and speech interruption. We show that the optimized parameters of wSTMI may be interpreted in terms of modulation transfer functions of the human auditory system. Thus, the proposed approach offers evidence affirming previous studies of the perceptual characteristics underlying speech signal intelligibility.

[Audiometric test battery for presbycusis]

Old people often complain that they can no longer sufficiently participate in communication with spoken language. The reasons for this lie in pathophysiological processes as well as in acoustic parameters and the decline in cognitive performance that frequently occurs in old age, which together severely limit the individual benefits of speech. Age-related hearing loss consists of a variety of pathophysiological and cognitive factors. Several audiometric procedures are necessary for profound diagnostics, planning and implementation of interventions for hearing improvement as well as interventions for the individual improvement of the benefits of hearing in everyday life. In a basic test battery, the subjective and objective procedures for the primary detailed quantification and differentiation of the pathophysiological effects of presbycusis are listed, which serve as a basis for interventions to improve hearing. If necessary, audiometric procedures for more in-depth pathophysiological analyses can be used as part of the extended test battery. They are mainly used to differentiate between peripheral and retrocochlear factors of age-related hearing loss. The aim of the methods in the test battery for the evaluation of communication impairment in everyday life is the quantitative and qualitative evaluation of the ability to participate in communication with spoken language under realistic acoustic everyday conditions. From the results, acoustic and cognitive factors can be identified which determine the limited benefits of speech. Thus, strategies and procedures for the improvement of speech communication can be derived which, despite the pathophysiological conditions, can lead to an improved participation in speech communication in the everyday life of the patients.