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Author: Alexandra MacPherson
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Languages : en
Pages : 0
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Older listeners often report difficulties understanding speech in noisy environments. Increasing the level of the speech relative to the background - e.g. by way of a hearing aid - usually leads to an increase in intelligibility. The amount of perceptual benefit that can be gained from a given improvement in signal-to-noise ratio (SNR), however, is not fixed: it instead depends entirely on the slope of the psychometric function. The shallower the slope, the less benefit the listener will receive. The aim of the research presented in this thesis was to better understand the factors which lead to shallow slopes. A systematic survey of published psychometric functions considered the factors which affect slope. Speech maskers, modulated-noise maskers, and target/masker confusability were all found to contribute to shallow slopes. Experiment 1 examined the role of target/masker confusion by manipulating masker intelligibility. Intelligible maskers were found to give shallower slopes than unintelligible ones but subsequent acoustic analysis demonstrated that modulation differences between the maskers were responsible for this effect. This was supported by the fact that the effect was seen at low SNRs. Experiment 2 confirmed that the effects of modulation and target/masker confusion occur at different SNRs. Experiments 3 and 4 demonstrated that directing attention to the target speech could "undo" the effects of target/masker confusion. In Experiments 5 and 6 a new method was developed to study whether slope effects are relevant to "real-world" situations. The results suggested that using continuous speech targets gave shallower slopes than standard speech-in-noise tests. There was little evidence found to suggest that shallow slopes are exacerbated for older or hearing-impaired listeners. It is concluded that in the complex demands of everyday listening environments the perceptual benefit received from a given gain in SNR may be considerably less than would be predicted by standard speech-in-noise paradigms.
Author: Alexandra MacPherson
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ISBN:
Category :
Languages : en
Pages : 0
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Older listeners often report difficulties understanding speech in noisy environments. Increasing the level of the speech relative to the background - e.g. by way of a hearing aid - usually leads to an increase in intelligibility. The amount of perceptual benefit that can be gained from a given improvement in signal-to-noise ratio (SNR), however, is not fixed: it instead depends entirely on the slope of the psychometric function. The shallower the slope, the less benefit the listener will receive. The aim of the research presented in this thesis was to better understand the factors which lead to shallow slopes. A systematic survey of published psychometric functions considered the factors which affect slope. Speech maskers, modulated-noise maskers, and target/masker confusability were all found to contribute to shallow slopes. Experiment 1 examined the role of target/masker confusion by manipulating masker intelligibility. Intelligible maskers were found to give shallower slopes than unintelligible ones but subsequent acoustic analysis demonstrated that modulation differences between the maskers were responsible for this effect. This was supported by the fact that the effect was seen at low SNRs. Experiment 2 confirmed that the effects of modulation and target/masker confusion occur at different SNRs. Experiments 3 and 4 demonstrated that directing attention to the target speech could "undo" the effects of target/masker confusion. In Experiments 5 and 6 a new method was developed to study whether slope effects are relevant to "real-world" situations. The results suggested that using continuous speech targets gave shallower slopes than standard speech-in-noise tests. There was little evidence found to suggest that shallow slopes are exacerbated for older or hearing-impaired listeners. It is concluded that in the complex demands of everyday listening environments the perceptual benefit received from a given gain in SNR may be considerably less than would be predicted by standard speech-in-noise paradigms.
Author: Alexandra MacPherson
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Category :
Languages : en
Pages :
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Author: Jane Smart
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Languages : en
Pages :
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ABSTRACT: Clear speech is a form of communication that talkers naturally use when speaking in difficult listening conditions or with a person who has a hearing loss. Clear speech, on average, provides listeners with hearing impairments an intelligibility benefit of 17 percentage points (Picheny, Durlach, & Braida, 1985) over conversational speech. In addition, it provides increased intelligibility in various listening conditions (Krause & Braida, 2003, among others), with different stimuli (Bradlow & Bent, 2002; Gagne, Rochette, & Charest, 2002; Helfer, 1997, among others) and across listener populations (Bradlow, Kraus, & Hayes, 2003, among others). Recently, researchers have attempted to compare their findings with clear and conversational speech, at slow and normal rates, with results from other investigators' studies in an effort to determine the relative benefits of clear speech across populations and environments. However, relative intelligibility benefits are difficult to determine unless baseline performance levels can be equated, suggesting that listener psychometric functions with clear speech are needed. The purpose of this study was to determine how speech intelligibility, as measured by percentage key words correct in nonsense sentences by young adults, varies with changes in speaking condition, talker and signal-to-noise ratio (SNR). Forty young, normal hearing adults were presented with grammatically correct nonsense sentences at five SNRs. Each listener heard a total of 800 sentences in four speaking conditions: clear and conversational styles, at slow and normal rates (i.e., clear/slow, clear/normal, conversational/slow, and conversational/normal). Overall results indicate clear/slow and conversational/slow were the most intelligible conditions, followed by clear/normal and then conversational/normal conditions. Moreover, the average intelligibility benefit for clear/slow, clear/normal and conversational/slow conditions (relative to conversational/normal) was maintained across an SNR range of -4 to 0 dB in the middle, or linear, portion of the psychometric function. However, when results are examined by talker, differences are observed in the benefit provided by each condition and in how the benefit varies across noise levels. In order to counteract talker variability, research with a larger number of talkers is recommended for future studies.
Author: Acoustical Society of America
Publisher:
ISBN:
Category : Acoustical engineering
Languages : en
Pages : 988
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Author: Jont B. Allen
Publisher: Morgan & Claypool Publishers
ISBN: 1598290096
Category : Technology & Engineering
Languages : en
Pages : 136
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Immediately following the Second World War, between 1947 and 1955, several classic papers quantified the fundamentals of human speech information processing and recognition. In 1947 French and Steinberg published their classic study on the articulation index. In 1948 Claude Shannon published his famous work on the theory of information. In 1950 Fletcher and Galt published their theory of the articulation index, a theory that Fletcher had worked on for 30 years, which integrated his classic works on loudness and speech perception with models of speech intelligibility. In 1951 George Miller then wrote the first book Language and Communication, analyzing human speech communication with Claude Shannon's just published theory of information. Finally in 1955 George Miller published the first extensive analysis of phone decoding, in the form of confusion matrices, as a function of the speech-to-noise ratio. This work extended the Bell Labs' speech articulation studies with ideas from Shannon's Information theory. Both Miller and Fletcher showed that speech, as a code, is incredibly robust to mangling distortions of filtering and noise. Regrettably much of this early work was forgotten. While the key science of information theory blossomed, other than the work of George Miller, it was rarely applied to aural speech research. The robustness of speech, which is the most amazing thing about the speech code, has rarely been studied. It is my belief (i.e., assumption) that we can analyze speech intelligibility with the scientific method. The quantitative analysis of speech intelligibility requires both science and art. The scientific component requires an error analysis of spoken communication, which depends critically on the use of statistics, information theory, and psychophysical methods. The artistic component depends on knowing how to restrict the problem in such a way that progress may be made. It is critical to tease out the relevant from the irrelevant and dig for the key issues. This will focus us on the decoding of nonsense phonemes with no visual component, which have been mangled by filtering and noise. This monograph is a summary and theory of human speech recognition. It builds on and integrates the work of Fletcher, Miller, and Shannon. The long-term goal is to develop a quantitative theory for predicting the recognition of speech sounds. In Chapter 2 the theory is developed for maximum entropy (MaxEnt) speech sounds, also called nonsense speech. In Chapter 3, context is factored in. The book is largely reflective, and quantitative, with a secondary goal of providing an historical context, along with the many deep insights found in these early works.
Author: Katherine Pelley
Publisher:
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Category :
Languages : en
Pages :
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ABSTRACT: While a majority of deaf students mainstreamed in public schools rely on interpreters, little research has investigated interpreter skills and no research to date has focused on interpreter intelligibility (Kluwin & Stewart, 2001). This thesis is the second in a series of experiments designed to quantify the contribution of various factors affecting the intelligibility of interpreters (transliterators) who use English-based communication modes. In the first experiment, 12 Cued Speech transliterators were asked to transliterate an audio lecture. Two aspects of these transliterated performances were then analyzed: 1) accuracy, as measured as the percent-correct cues produced, and 2) lag time, the average delay between lecture and transliterated message. For this thesis, eight expert receivers of Cued Speech were presented with visual stimuli from the transliterated messages and asked to transcribe the stimuli. Intelligibility was measured as the percentage of words correctly received. Results show a positive nonlinear relationship exits between transliterator accuracy and message intelligibility. Intelligibility improved with accuracy at the same rate for both novice and veteran transliterators, but receiver task difficulty was less for stimuli produced by veterans than novices (as evidenced by a left shift in the psychometric function for veterans compared to novices). No large effects of lag time were found in the accuracy-intelligibility relationship, but an "optimal lag time" range was noted from 1 to 1.5 seconds, for which intelligibility scores were higher overall. Intelligibility scores were generally higher than accuracy, but not all transliterators followed the same accuracy-intelligibility pattern due to other sources of variability. Possible sources of transliterator variability included rate of cueing, visible speech clarity, facial expression, timing (to show syllable stress or word emphasis), cueing mechanics, and mouth-cue synchronization. Further research is needed to determine the impact these factors have on intelligibility so that future transliterator training and certification can focus on all factors necessary to ensure highly intelligible Cued Speech transliterators.
Author: Mary Rudner
Publisher: Frontiers Media SA
ISBN: 2889662187
Category : Science
Languages : en
Pages : 337
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Author: Arthur M. Jacobs
Publisher: Frontiers Media SA
ISBN: 288971148X
Category : Science
Languages : en
Pages : 142
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Author: Sarah Yoho Leopold
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The three manuscripts presented here examine the relative importance of various `critical bands’ of speech, as well as their susceptibility to the corrupting influence of background noise. In the first manuscript, band-importance functions derived using a novel technique are compared to the standard functions given by the Speech Intelligibility Index (ANSI, 1997). The functions derived with the novel technique show a complex 'microstructure' not present in previous functions, possibly indicating an increased accuracy of the new method. In the second manuscript, this same technique is used to examine the effects of individual talkers and types of speech material on the shape of the band-importance functions. Results indicate a strong effect of speech material, but a smaller effect of talker. In addition, the use of ten talkers of different genders appears to greatly diminish any effect of individual talker. In the third manuscript, the susceptibility to noise of individual critical bands of speech was determined by systematically varying the signal-to-noise ratio in each band. The signal-to-noise ratio that resulted in a criterion decrement in intelligibility for each band was determined. Results from this study indicate that noise susceptibility is not equal across bands, as has been assumed. Further, noise susceptibility appears to be independent of the relative importance of each band. Implications for future applications of these data are discussed.
Author: Joshua M. Alexander
Publisher:
ISBN:
Category :
Languages : en
Pages : 298
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