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

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.

Background: In certain masking paradigms, the masker can have two components, energetic and informational. Energetic masking is the traditional peripheral masking, whereas informational masking involves confusions (uncertainty) between the signal and masker that originate more centrally in the auditory system. Sperry et al (1997) used Northwestern University Auditory Test No. 6 (NU-6) words in multitalker babble to study the differential effects of energetic and informational masking using babble played temporally forward (FB) and backward (BB). The FB and BB are the same except BB is void of the contextual and semantic content cues that are available in FB. It is these informational cues that are thought to fuel informational masking. Sperry et al found 15% better recognition performance (∼3 dB) on BB than on FB, which can be interpreted as the presence of informational masking in the FB condition and not in the BB condition (Dirks and Bower, 1969). The Words-in-Noise Test (WIN) (Wilson, 2003; Wilson and McArdle, 2007) uses NU-6 words as the signal and multitalker babble as the masker, which is a combination of stimuli that potentially could produce informational masking. The WIN presents 5 or 10 words at each of seven signal-to-noise ratios (S/N, SNR) from 24 to 0 dB in 4 dB decrements with the 50% correct point being the metric of interest. The same recordings of the NU-6 words and multitalker babble used by Sperry et al are used in the WIN. Purpose: To determine whether informational masking was involved with the WIN. Research Design: Descriptive, quasi-experimental designs were conducted in three experiments using FB and BB in various paradigms in which FB and BB varied from 4.3 sec concatenated segments to essentially continuous. Study Sample: Eighty young adults with normal hearing and 64 older adults with sensorineural hearing losses participated in a series of three experiments. Data Collection and Analysis: Experiment 1 compared performance on the normal WIN (FB) with performance on the WIN in which the babble segment with each word was reversed temporally (BB). Experiment 2 examined the effects of continuous FB and BB segments on WIN performance. Experiment 3 replicated the Sperry et al (1997) experiment at 4 and 0 dB S/N using NU-6 words in the FB and BB conditions. Results: Experiment 1-with the WIN paradigm, recognition performances on FB and BB were the same for listeners with normal hearing and listeners with hearing loss, except at the 0 dB S/N with the listeners with normal hearing at which performance was significantly better on BB than FB. Experiment 2-recognition performances on FB and BB were the same at all SNRs for listeners with normal hearing using a slightly modified WIN paradigm. Experiment 3-there was no difference in performances on the FB and BB conditions with either of the two SNRs. Conclusions: Informational masking was not involved in the WIN paradigm. The Sperry et al results were not replicated, which is thought to be related to the way in which the Sperry et al BB condition was produced.

No description available.