It is often difficult for people to understand speech when there are other ongoing conversations in the background. This dissertation investigates how different background maskers interfere with our ability to comprehend speech and the reasons why older listeners have more difficulties than younger listeners in these tasks. An ecologically valid approach was applied: instead of words or short sentences, participants were presented with two fairly lengthy lectures simultaneously, and their task was to listen to the target lecture, and ignore the competing one. Afterwards, they answered questions regarding the target lecture. Experiment 1 found that both normal-hearing and hearing-impaired older adults performed poorer than younger adults when everyone was tested in identical listening situations. However, when the listening situation was individually adjusted to compensate for age-related differences in the ability to recognize individual words in noise, age-related difference in comprehension disappeared. Experiment 2 compared the masking effects of a single-talker competing lecture to a babble of 12 voices, and the signal-to-noise ratio (SNR) was manipulated so that the masker was either of similar volume as the target, or much louder. The results showed that the competing speech was much more distracting than babble. Moreover, increasing the masker level negatively affected speech comprehension only when the masker was babble; when it was a single-talker lecture, the performance plateaued as the SNR decreased from -2 to -12 dB. Experiment 3 compared the effects of semantic content and acoustic similarity on speech comprehension by comparing a normal speech masker with a time-reversed one (to examine the effect of semantic content) and a normal speech masker with an 8-band vocoded speech (to examine the effect of acoustic similarity). The results showed that both semantic content and acoustic similarity contributed to informational masking, but the latter seemed to play a bigger role than the former. Together, the results indicated that older adults’ speech comprehension difficulties with maskers were mainly due to declines in their hearing capacities rather than their cognitive functions. The acoustic similarity between the target and competing speech may be the main reason for informational masking, with semantic interference playing a secondary role.

Competing speech seems to pose a greater challenge to spoken language comprehension than does competing noise, especially for older adults. The difficulties of older adults may be due to declines in auditory and cognitive processing. However, evidence suggests that the use of top-down information processing to overcome this interference may be preserved in aging. This research investigated the effect of speech- and noise masking on language comprehension, as well as age-related differences in the use of top-down processing to overcome masking. Topic I examined whether younger and older adults gain the same release from masking given a partial preview of a target sentence in quiet (auditory prime) prior to hearing the full sentence in noise, and investigated the auditory factors contributing to the advantage provided by the primes. Results showed that despite age-related declines in overall performance, younger and older listeners benefited similarly from priming. This benefit was not attributable to cues about the target talker’s voice or fluctuations in the amplitude envelope of the target sentences. Topics II and III examined the effect of speech- and noise masking on the time-course of stream segregation. The analyses revealed that stream segregation takes time to build up when a speech target is masked by other speech, but not when it is masked by noise. Subsequent analyses showed that in younger adults, the delay in segregation under speech masking was primarily due to the vocal similarities between the talkers, with interference from the semantic content of the masker playing a secondary role in impeding performance. The results also showed that older listeners were less efficient than younger listeners in segregating speech from speech-like maskers. Furthermore, older listeners benefited less than younger listeners when the amplitude envelope modulations of maskers were limited. Overall, the findings indicate that some of the language comprehension difficulties experienced by older listeners in noisy environments may be due to age-related declines in stream segregation and a decreased ability to benefit from fluctuations in the amplitude envelopes of maskers. However, benefit from priming may help offset some of these age-related declines in auditory scene analysis.

It is often difficult for people to understand speech when there are other ongoing conversations in the background. This dissertation investigates how different background maskers interfere with our ability to comprehend speech and the reasons why older listeners have more difficulties than younger listeners in these tasks. An ecologically valid approach was applied: instead of words or short sentences, participants were presented with two fairly lengthy lectures simultaneously, and their task was to listen to the target lecture, and ignore the competing one. Afterwards, they answered questions regarding the target lecture. Experiment 1 found that both normal-hearing and hearing-impaired older adults performed poorer than younger adults when everyone was tested in identical listening situations. However, when the listening situation was individually adjusted to compensate for age-related differences in the ability to recognize individual words in noise, age-related difference in comprehension disappeared. Experiment 2 compared the masking effects of a single-talker competing lecture to a babble of 12 voices, and the signal-to-noise ratio (SNR) was manipulated so that the masker was either of similar volume as the target, or much louder. The results showed that the competing speech was much more distracting than babble. Moreover, increasing the masker level negatively affected speech comprehension only when the masker was babble; when it was a single-talker lecture, the performance plateaued as the SNR decreased from -2 to -12 dB. Experiment 3 compared the effects of semantic content and acoustic similarity on speech comprehension by comparing a normal speech masker with a time-reversed one (to examine the effect of semantic content) and a normal speech masker with an 8-band vocoded speech (to examine the effect of acoustic similarity). The results showed that both semantic content and acoustic similarity contributed to informational masking, but the latter seemed to play a bigger role than the former. Together, the results indicated that older adults’ speech comprehension difficulties with maskers were mainly due to declines in their hearing capacities rather than their cognitive functions. The acoustic similarity between the target and competing speech may be the main reason for informational masking, with semantic interference playing a secondary role.

Competing speech seems to pose a greater challenge to spoken language comprehension than does competing noise, especially for older adults. The difficulties of older adults may be due to declines in auditory and cognitive processing. However, evidence suggests that the use of top-down information processing to overcome this interference may be preserved in aging. This research investigated the effect of speech- and noise masking on language comprehension, as well as age-related differences in the use of top-down processing to overcome masking. Topic I examined whether younger and older adults gain the same release from masking given a partial preview of a target sentence in quiet (auditory prime) prior to hearing the full sentence in noise, and investigated the auditory factors contributing to the advantage provided by the primes. Results showed that despite age-related declines in overall performance, younger and older listeners benefited similarly from priming. This benefit was not attributable to cues about the target talker’s voice or fluctuations in the amplitude envelope of the target sentences. Topics II and III examined the effect of speech- and noise masking on the time-course of stream segregation. The analyses revealed that stream segregation takes time to build up when a speech target is masked by other speech, but not when it is masked by noise. Subsequent analyses showed that in younger adults, the delay in segregation under speech masking was primarily due to the vocal similarities between the talkers, with interference from the semantic content of the masker playing a secondary role in impeding performance. The results also showed that older listeners were less efficient than younger listeners in segregating speech from speech-like maskers. Furthermore, older listeners benefited less than younger listeners when the amplitude envelope modulations of maskers were limited. Overall, the findings indicate that some of the language comprehension difficulties experienced by older listeners in noisy environments may be due to age-related declines in stream segregation and a decreased ability to benefit from fluctuations in the amplitude envelopes of maskers. However, benefit from priming may help offset some of these age-related declines in auditory scene analysis.

Auditory maskers, whether intelligible speech or unintelligible noise, can make it difficult to hear and/or process a target sentence. These maskers can present challenges to peripheral processing as well as central processing. Change in pupil size is a physiological index of listening effort and can be measured using eye tracking technology. The aim of the study was to compare listening effort, as measured by changes in pupil size in individuals with normal hearing, between the conditions of Intelligible Speech Masker (ISM), Speech Shaped, Speech Envelope-Modulated Noise Maskers (SSSNM), and Stationary Noise Masker (SNM). Spatial separation between target and maskers was used throughout all conditions. The study design used adaptive tracks that varied the Target to Masker Ratios (TMRs) in each of the 3 conditions in order to identify the TMR corresponding to the 75% correct point on the psychometric function for each participant. Once the TMR corresponding to the 75% correct point was identified, this TMR was held constant for 24 trials while pupil size was recorded. The results show that the ISM condition elicited a higher degree of listening effort compared to either of the noise conditions (SNM and SSSNM). These results reveal that more effort is required to ignore background speech than to ignore background noise at equivalent TMRs. Understanding the amount of effort that young, normal-hearing listeners must exert in these different types of situations will provide a foundation for later measuring the amount of effort that individuals with hearing loss and/or cognitive-linguistic deficits (e.g., aphasia) must exert in the same situations. / 2023-05-19T00:00:00Z

No description available.

No description available.

A recent study by Polka, Rvachew, and Molnar (2008) found that 6- to 8-month-old infants do not discriminate a simple native consonant-vowel contrast when familiarized to it in the presence of distraction noise (i.e., recordings of crickets and birds chirping), even when testing was conducted in quiet. Because the distraction noise did not overlap with the phonemes' frequencies, failure to encode the familiarization phoneme could be due more to a disruption in infant attention than to direct masking effects. Given that infants learn speech under natural conditions involving noise and distraction, it is important to identify factors that may 'protect' their speech perception under non-ideal listening conditions. The current study investigated three possible factors: speech register, face information, and speaker gender. Six-month-old infants watched a video of a female speaker producing a native phoneme in either an adult-directed or infant-directed manner accompanied by the same background noise as in Polka et al. (2008). After habituation, infants were tested with alternating trials of the familiar phoneme and a novel phoneme in quiet. Phoneme discrimination was measured by recording infants' heart rate and looking times during familiar and novel trials. Discrimination was poor in infants who viewed a female speaker using adult-directed speech but was significantly improved (as seen in both dependent measures of attention) when the female speaker used infant-directed speech. Results indicate that common factors in the typical environment of infants can promote speech perception abilities in noise. / Master of Science

No description available.

The study investigated the effects of noise, one of the major environmental stressors, on speech perception and spoken word comprehension. Three tasks were employed – listening span, listening comprehension, and shadowing – in order to find out to what extent different types of background noise affected speech perception and encoding into working verbal memory, as well as spoken word comprehension. Six types of maskers were used – (1) single babble masker in English, (2) single babble masker in Mandarin, (3) multi babble masker in Greek and (4) construction site noise, (5) narrow-band speech signal emulating phone effect and (6) reverberated speech signal. These could be categorized as energetic (2, 3, and 4), informational (1) and signal degradation (6 and 7) noise maskers. The study found that general speech perception and specific word comprehension are not equally affected by the different noise maskers – if shadowing is considered primarily a task relying on speech perception, with the other two tasks considered to rely on working memory, word comprehension and semantic inference. The results indicate that informational masking is most detrimental to speech perception, while energetic masking and sound degradation are most detrimental to spoken word comprehension. The results imply that masking categories must be used with caution, since not all maskers belonging to one category had the same effect on performance. Finally, introducing a noise component to any memory task, particularly to speech perception and spoken word recognition tasks, adds another cognitively stimulating real-life dimension to them. This could be beneficial to students training to become interpreters helping them to get accustomed to working in a noisy environment, an inevitable part of this profession. A final study explored the effects of noise on automatic speech recognition. The same types of noise as in the human studies were tested on two automatic speech recognition programs: Otter and Ava. This technology was originally developed as an aid for the deaf and hard of hearing. However, their application has since been extended to a broad range of fields, including education, healthcare and finance. The analysis of the transcripts created by the two programs found speech to text technology to be fairly resilient to the degradation of the speech signal, while mechanical background noise still presented a serious challenge to this technology. / Dissertation / Doctor of Philosophy (PhD) / The study investigated the effects of noise, one of the major environmental stressors, on speech perception and spoken word comprehension. Throughout three different tasks (listening span task, in which participants were asked to recall a certain number of items from a list; listening comprehension task, in which listeners needed to demonstrate understanding of the incoming speech; and shadowing, in which listeners were required to listen and simultaneously repeat aloud the incoming speech), various types of background noise were presented in order to find out which ones would cause more disruptions to the two cognitive processes. The study found that general speech perception and specific word comprehension are not equally affected by the different noise maskers – provided that shadowing is considered primarily a task relying on speech perception, with the other two tasks considered to rely on working memory, word comprehension and semantic inference, or the way the listener combines and synthesizes information from different parts of a text (or speech) in order to establish its meaning. The results indicate that understandable background speech is most detrimental to speech perception, while any type of noise, if loud enough, as well as degraded target speech signal are most detrimental to spoken word comprehension. Finally, introducing a noise component to these tasks, adds another cognitively stimulating real-life dimension, which could potentially be beneficial to students of interpreting by getting them accustomed to working in a noisy environment, an inevitable part of this profession. Another field of application is the optimization of speech recognition software. In the last study, the same types of noise as used in the first studies were tested on two automatic speech recognition programs. This technology was originally developed as an aid for the deaf and hard of hearing. However, its application has since been extended to a broad range of fields including education, healthcare and finance. The analysis of the transcripts created by the two programs found speech to text technology to be fairly resilient to a degraded speech signal, while mechanical background noise still presented a serious challenge to this technology.