Newborns were once viewed as having the ability to distinguish between all possible speech contrasts present in the world’s languages. However, recent work suggests that this view is an oversimplification of young infants’ perceptual abilities. This study used the Stimulus Alternation Preference Procedure (SAPP) to examine 6- and 10- month-old infants’ ability to discriminate between voiced and voiceless stops (lexically contrastive in English) as well as voiced and pre-voiced stops (not lexically contrastive in English). Six-month-olds distinguished between voiced and voiceless stops, but not between voiced and pre-voiced stops. Ten-month-olds failed to discriminate either contrast. We tentatively conclude that 1) pre-voicing may be a subtle contrast requiring experience to perceive, and 2) the SAPP might not be an ideal method to examine discrimination abilities in 10-month-olds.

Newborns were once viewed as having the ability to distinguish between all possible speech contrasts present in the world’s languages. However, recent work suggests that this view is an oversimplification of young infants’ perceptual abilities. This study used the Stimulus Alternation Preference Procedure (SAPP) to examine 6- and 10- month-old infants’ ability to discriminate between voiced and voiceless stops (lexically contrastive in English) as well as voiced and pre-voiced stops (not lexically contrastive in English). Six-month-olds distinguished between voiced and voiceless stops, but not between voiced and pre-voiced stops. Ten-month-olds failed to discriminate either contrast. We tentatively conclude that 1) pre-voicing may be a subtle contrast requiring experience to perceive, and 2) the SAPP might not be an ideal method to examine discrimination abilities in 10-month-olds.

When listeners are presented with stimuli from multiple speakers versus single speakers in a perception experiment, decreased speech recognition accuracy and increased response time results. These findings have been demonstrated in studies that have employed normal (Creelman, 1957; Mullennix & Pisoni, 1990; Nygaard & Pisoni, 1998) and accented speech (Bradlow & Bent, 2008). It is thought that perceptual normalisation processes are, in part, responsible for this perceptual cost (Bladon, Henton, & Pickering, 1984; Johnson, 2009; Magnuson & Nusbaum, 2007; Mullennix, Pisoni, & Martin, 1989). Interestingly, studies are yet to examine whether these same findings occur when listeners encounter dysarthric speech – a naturally degraded speech signal associated with neurological disorder or disease. It has also been found that when listeners are exposed to multiple speakers with dysarthria, they generally adapt to the dysarthric signal over time; resulting in an improved ability to decipher the signal (Liss, Spitzer, Caviness, & Adler, 2002; Tjaden & Liss, 1995a). However, the rate of this adaption when listeners are exposed to a single speaker is yet to be examined. This study aimed to determine: (1) whether the intelligibility of dysarthric speech (in this case, hypokinetic dysarthria associated with Parkinson‘s disease) varied across single versus multi-speaker conditions; and (2) whether intelligibility increased over time when a listener was exposed to a single speaker with dysarthria. To answer these questions, sixty young healthy listeners were randomly allocated to one of four experimental conditions, one multiple speaker and three single speaker conditions. Each listener transcribed 60 three to five word phrases over one session and the results were examined for percent words correct. Contrary to expectations, there was no significant difference in percent intelligibility scores of the listener group who transcribed in a multi-speaker versus transcriptions from the single speaker listener conditions. In addition, perceptual learning effects across the rating period were identified for two out of the three single speaker listener groups only. The absence of significant findings in the multi-speaker versus single speaker transcripts may be explained by further analysis of within speaker variability. Acoustic analysis of the speakers may also shed light on the reduced perceptual learning that occurred in one of the single speaker groups. Greater numbers of speakers and experimental phrases would be beneficial in expanding trends seen in intelligibility of the single speaker groups.

The main purpose of this research was to develop a screening test for speech discrimination ability. Twenty-five of the most difficult CID W-22 words were chosen for the material. These words were presented live voice without a carrier phrase, recorded with a carrier phrase, and recorded without a carrier phrase. These scores were then compared to the CID 4-22 score, Two groups of twenty subjects were tested: one group of normal hearing young adults and one group of subjects with sensors-neural hearing losses.All three experimental versions of the screening test yield a valid indication of the listener's speech discrimination ability. Any listener scoring 80% or better on the screening test has essentially normal discrimination ability.

The hypothesis was proposed that hard of hearing individuals are able to understand men's voices better than women's voices relative to the understanding of the same voices by normal hearers. Eighteen normal and eighteen hard of hearing subjects participated in a study designed to demonstrate the relationship between sex and intelligibility of speaker for hard of hearing persons compared to normal hearing individuals. Discrimination scores were obtained with both a male and a female speaker under both quiet and noisy listening conditions. Analysis of variance techniques revealed that no significant difference in discrimination scores occurred due to sex of speaker when the hard of hearing subjects were compared with the normal hearers. Further examination of the data indicated that neither extent nor configuration of hearing loss influenced the relative intelligibility of male and female voices for hard of hearing persons. No evidence was found to support the hypothesis.

No description available.

This study investigates the correlations between phonetic, perceptual and auditory spaces of fricatives. These spatial representations are constructed from estimated distances between fricatives in each domain. The present work is an extension of previous studies with vowels, which showed a close association between the auditory and perceptual spaces. The dimensions obtained were highly related to the formant frequencies of the vowels and their phonetic (articulatory) descriptions. However, these findings could have been anticipated due to inherent similarities in articulatory and acoustic forms of vowels. No corresponding relationships for consonants have yet been established, and it is important to investigate whether such relationships might also hold for consonants, since their acoustic form is not so simply linked to their phonetic (articulatory) form. In this study we relate 'places of articulation' for fricatives with their spectral characteristics and perceptual similarities to investigate any articulatory references to their perception. A variety of fricative and fricative-like stimuli were examined. Perceptual distances were derived from subjective judgments of the similarities between the fricatives. Auditory distances were obtained from critical bandpass filter banks and distance metrics were applied to model the spectral processing in the auditory periphery. The distances in the perceptual and auditory spaces were analysed using multidimensional scaling in order to test their correlation and how it varied according to the naturalness of the stimulus materials. The relations between the spaces were measured quantitatively by canonical correlation analyses. The acoustic correlates of these spatial dimensions were also identified. The perceptual dimensions of the most natural fricative stimuli proved to be highly related to both their phonetic (articulatory) and auditory spaces. By demonstrating a link across these domains, the study, therefore, favours perceptual theories of a unified nature, rather than the views based on 'strong articulatory' or 'strong auditory' modes of speech perception.

No description available.

This work includes several studies exploring functional specialization of human primary and anterior secondary auditory cortex (AC) in the two hemispheres. It was hypothesized that the left hemisphere prepotency for linguistic processing is based, in part, on specialized mechanisms within this hemisphere for the processing of acoustic transients relevant to speech. Evidence supporting this idea was obtained in a positron emission tomography study (PET). Since nonlinguistic stimuli were used, the observed left-hemispheric activation cannot be specific to the speech system, but must reflect a more general processing mechanism. A reanalysis of data from six auditory PET studies revealed that the peak focus of auditory activation was significantly posterior to Heschl's gyrus (HG) in the right hemisphere, while it encompassed HG in the left. The cause of this asymmetry is unknown, but it appears to hold true for other auditory functional imaging studies in the literature. Functional specialization in auditory regions was also explored by testing patients with anterior temporal-lobe resections from either the left (LT) or right (RT) hemisphere and normal volunteers on several linguistic and nonlinguistic auditory tasks. The excisions in these patients always included some secondary AC, and sometimes included primary AC (HG). I had speculated that anterior. secondary AC in the left hemisphere was specialized for processing word-sounds, but patients with excisions in this area were unimpaired in their ability to use such information to retrieve items from the mental lexicon. Furthermore these patients did not show a disproportionate impairment on a lexical decision task, when items were presented aurally instead of visually, compared to normal subjects. With few exceptions, a battery of psychophysical tests of auditory processes were performed normally by all groups. The notable exception was an impairment in the group of RT patients with lesions that included HG on a ta

Thesis (Ph.D.) OGI School of Science & Engineering at OHSU, March 2008. / Includes bibliographical references (leaves 99 - 108).