Predicting speech-in-speech recognition: Short-term audibility and spatial separation.

Quantifying the factors that predict variability in speech-in-speech recognition represents a fundamental challenge in auditory science. Stimulus factors associated with energetic and informational masking (IM) modulate variability in speech-in-speech recognition, but energetic effects can be difficult to estimate in spectro-temporally dynamic speech maskers. The current experiment characterized the effects of short-term audibility and differences in target and masker location (or perceived location) on the horizontal plane for sentence recognition in two-talker speech. Thirty young adults with normal hearing (NH) participated. Speech reception thresholds and keyword recognition at a fixed signal-to-noise ratio (SNR) were measured in each spatial condition. Short-term audibility for each keyword was quantified using a glimpsing model. Results revealed that speech-in-speech recognition depended on the proportion of audible glimpses available in the target + masker keyword stimulus in each spatial condition, even across stimuli presented at a fixed global SNR. Short-term audibility requirements were greater for colocated than spatially separated speech-in-speech recognition, and keyword recognition improved more rapidly as a function of increases in target audibility with spatial separation. Results indicate that spatial cues enhance glimpsing efficiency in competing speech for young adults with NH and provide a quantitative framework for estimating IM for speech-in-speech recognition in different spatial configurations.

Predicting speech-in-speech recognition: Short-term audibility, talker sex, and listener factors.

Speech-in-speech recognition can be challenging, and listeners vary considerably in their ability to accomplish this complex auditory-cognitive task. Variability in performance can be related to intrinsic listener factors as well as stimulus factors associated with energetic and informational masking. The current experiments characterized the effects of short-term audibility of the target, differences in target and masker talker sex, and intrinsic listener variables on sentence recognition in two-talker speech and speech-shaped noise. Participants were young adults with normal hearing. Each condition included the adaptive measurement of speech reception thresholds, followed by testing at a fixed signal-to-noise ratio (SNR). Short-term audibility for each keyword was quantified using a computational glimpsing model for target+masker mixtures. Scores on a psychophysical task of auditory stream segregation predicted speech recognition, with stronger effects for speech-in-speech than speech-in-noise. Both speech-in-speech and speech-in-noise recognition depended on the proportion of audible glimpses available in the target+masker mixture, even across stimuli presented at the same global SNR. Short-term audibility requirements varied systematically across stimuli, providing an estimate of the greater informational masking for speech-in-speech than speech-in-noise recognition and quantifying informational masking for matched and mismatched talker sex.

Spoken narrative comprehension for young adult listeners: effects of competing voices and noise.

OBJECTIVE: To examine the influence of competing voices or noise on the comprehension of spoken narratives for young adults. DESIGN: First, an intelligibility assessment of the target narratives was conducted to establish a signal-to-noise ratio ensuring accurate initial speech recognition. Then, narrative comprehension for two target types (fixed and varied target talker) was measured in four listening conditions (quiet, one-talker speech, speech babble, speech-shaped noise). After hearing target narratives in each listening condition, participants completed a visual recognition memory task that assessed the comprehension of the narrative materials at three levels of representation (surface form, propositional, event model). STUDY SAMPLE: Seventy adults (18-32 years of age). RESULTS: Narrative comprehension results revealed a main effect of listening condition at the event model level, indicating poorer narrative memory of described situations for all noise conditions compared to quiet. Increased positive responses to thematically consistent but situationally "wrong" memory probes drove this effect. No other significant effects were observed. CONCLUSION: Despite near-perfect speech recognition, background noise negatively influenced aspects of spoken narrative comprehension and memory. Specifically, noise did not disrupt memory for what was said (surface form and propositional memory), but only memory for what was talked about (event model memory).

The effect of fundamental frequency contour similarity on multi-talker listening in older and younger adults.

Older adults with hearing loss have greater difficulty recognizing target speech in multi-talker environments than young adults with normal hearing, especially when target and masker speech streams are perceptually similar. A difference in fundamental frequency (f0) contour depth is an effective stream segregation cue for young adults with normal hearing. This study examined whether older adults with varying degrees of sensorineural hearing loss are able to utilize differences in target/masker f0 contour depth to improve speech recognition in multi-talker listening. Speech recognition thresholds (SRTs) were measured for speech mixtures composed of target/masker streams with flat, normal, and exaggerated speaking styles, in which f0 contour depth systematically varied. Computational modeling estimated differences in energetic masking across listening conditions. Young adults had lower SRTs than older adults; a result that was partially explained by differences in audibility predicted by the model. However, audibility differences did not explain why young adults experienced a benefit from mismatched target/masker f0 contour depth, while in most conditions, older adults did not. Reduced ability to use segregation cues (differences in target/masker f0 contour depth), and deficits grouping speech with variable f0 contours likely contribute to difficulties experienced by older adults in challenging acoustic environments.

The effect of target/masker fundamental frequency contour similarity on masked-speech recognition.

Greater informational masking is observed when the target and masker speech are more perceptually similar. Fundamental frequency (f0) contour, or the dynamic movement of f0, is thought to provide cues for segregating target speech presented in a speech masker. Most of the data demonstrating this effect have been collected using digitally modified stimuli. Less work has been done exploring the role of f0 contour for speech-in-speech recognition when all of the stimuli have been produced naturally. The goal of this project was to explore the importance of target and masker f0 contour similarity by manipulating the speaking style of talkers producing the target and masker speech streams. Sentence recognition thresholds were evaluated for target and masker speech that was produced with either flat, normal, or exaggerated speaking styles; performance was also measured in speech spectrum shaped noise and for conditions in which the stimuli were processed through an ideal-binary mask. Results confirmed that similarities in f0 contour depth elevated speech-in-speech recognition thresholds; however, when the target and masker had similar contour depths, targets with normal f0 contours were more resistant to masking than targets with flat or exaggerated contours. Differences in energetic masking across stimuli cannot account for these results.

Age-Related Changes in Objective and Subjective Speech Perception in Complex Listening Environments.

Purpose: A frequent complaint by older adults is difficulty communicating in challenging acoustic environments. The purpose of this work was to review and summarize information about how speech perception in complex listening situations changes across the adult age range. Method: This article provides a review of age-related changes in speech understanding in complex listening environments and summarizes results from several studies conducted in our laboratory. Results: Both degree of high frequency hearing loss and cognitive test performance limit individuals' ability to understand speech in difficult listening situations as they age. The performance of middle-aged adults is similar to that of younger adults in the presence of noise maskers, but they experience substantially more difficulty when the masker is 1 or 2 competing speech messages. For the most part, middle-aged participants in studies conducted in our laboratory reported as much self-perceived hearing problems as did older adult participants. Conclusions: Research supports the multifactorial nature of listening in real-world environments. Current audiologic assessment practices are often insufficient to identify the true speech understanding struggles that individuals experience in these situations. This points to the importance of giving weight to patients' self-reported difficulties. Presentation Video: http://cred.pubs.asha.org/article.aspx?articleid=2601619.