Multiple looks in speech sound discrimination in adults.

N. F. Viemeister and G. H. Wakefield's (1991) multiple looks hypothesis is a theoretical approach from the psychoacoustic literature that has promise for bridging the gap between results from speech perception research and results from psychoacoustic research. This hypothesis accounts for sensory detection data and predicts that if the "looks" at a stimulus are independent and information is combined optimally, sensitivity should increase for 2 pulses relative to 1 pulse. Specifically, d' (a bias-free measure of sensitivity) for 2 pulses should be larger than d' for 1 pulse. One speech discrimination paradigm that presents stimuli with multiple presentations is the change/no-change procedure. On a change trial, the standard and comparison stimuli differ; on a no-change trial, they are the same. Normal-hearing adults were tested using the change/no-change procedure with 3 consonant-vowel minimal pairs in combinations of 1, 2, and 4 repetitions of standard and comparison stimuli at various signal-to-noise ratios. If multiple looks extend to this procedure, performance should increase with higher repetition numbers. Performance increased with more presentations of the speech contrasts tested. The multiple looks hypothesis predicted performance better at low repetition numbers when performance was near d' values of 1.0 than at higher repetition numbers and higher performance levels.     

Developmental changes in speech discrimination in infants

A visually reinforced infant speech discrimination (VRISD) paradigm is described and evaluated. Infants at two ages were tested with the new paradigm on the following speech contrasts: [sa] vs [va], [sa] vs [fa], [sa] VS [za], [as] vs [a:s], vs [a:z], [at] vs [a:d], [a:t] vs [a:d], [at] vs [a:t], [fa] vs [thetaa]and [fi] vs [thetai]. The data reported are compared with data on the same speech contrasts obtained from three month olds in a high-amplitude sucking paradigm. Evidence suggesting developmental changes in speech-sound discriminatory ability is reported. Results are interpreted in light of salience of available acoustic cues and in terms of new methodological advances.     

A closed-set sentence protocol for assessing speech discrimination in deaf individuals: the speech sound pattern discrimination test

Forty hearing-impaired young adults were tested with a newly developed instrument designed to assess auditory speech processing skill. Analyses indicated that the resulting test data could be characterized in terms of the Rasch model for person measurement. Evidence of the scale's empirical validity also was obtained. The instrument uses a closed-set sentence discrimination task, and appears to be useful over a fairly wide range of hearing losses.     

Effects of aging on speech sound discrimination in the Mongolian gerbil

The of this study was to examine the hypothesis that aging would adversely effect speech sound discrimination in the Mongolian gerbil, as assessed by behavioral techniques. The involved measuring difference limens (DLs) for frequency changes along three synthetic speech continua (vowel, liquid, stop-consonant) in 25 gerbils as a function of age up to 36 mo. Absolute thresholds were also measured in the aging gerbils to verify normal hearing. The indicated no adverse effects of aging on the DLs for any of the speech continua. Thus the was that "intrinsic" aging processes in the gerbil, considered apart from "extrinsic" insulting factors, are not detrimental to speech discrimination, at least under quiet conditions. The clinical implications for humans are that the deficits typically observed in elderly humans for speech sound discrimination may be insult-related, and not the result of normal aging processes.     

Development of materials for the clinical assessment of speech recognition: the speech sound pattern discrimination test.

The purpose of this investigation was to evaluate the validity and reliability of materials designed for an assessment procedure capable of making meaningful distinctions in speech recognition ability among individuals having mild-to-moderate hearing losses. Sets of phonetic contrasts were presented within sentence contexts to 53 listeners (22 normal hearing, 31 hearing impaired) in 4 listening conditions (quiet and with background competition at signal-to-noise ratios of +5, 0, and -5 dB). The listeners were asked to discriminate pairs of sentences (e.g., "The man hid the dog" and "The man hit the dog") using same-different judgments. Their performances were analyzed in a manner enabling comparisons among items in terms of the classification of phonetic contrasts. Listener performance was also compared to performance on a set of independent variables, including the W-22 and QuickSIN speech tests, high-frequency hearing loss, speech reception threshold, listener age, and others. Results indicated that the new materials distinguished the normal-hearing from the hearing-impaired group and that listener performance (a) declined about 17% for each 5 dB decrement in SNR and (b) was influenced by the phonetic content of items in a manner similar to that reported by G. A. Miller and P. E. Nicely (1955). The performances of the hearing-impaired listeners were much more strongly related to high-frequency hearing loss, listener age, and other variables than were their performances on either the W-22 or QuickSIN tests. These findings are discussed with specific reference to the use of a mathematical model (i.e., the Rasch model for person measurement) for scaling items along a continuum of difficulty. The mathematical model and associated item difficulty values will serve as the basis for construction of a clinically useful computerized, adaptive test of speech recognition ability known as the Speech Sound Pattern Discrimination Test (Bochner, J., Garrison, W., Palmer, L., MacKenzie, D., & Braveman, A., 1997).     

Audio-visual discrimination of speech.

Tests utilizing audio-visual presentations of speech may have more significance than has hitherto been recognized. Such tests appear to offer more reliable, more realistic and more reproducible measures of communication impairments than either auditory speech discrimination tests, or visual speech discrimination tests.     

Perceptual discrimination of speech sounds in developmental dyslexia.

Experiments previously reported in the literature suggest that people with dyslexia have a deficit in categorical perception. However, it is still unclear whether the deficit is specific to the perception of speech sounds or whether it more generally affects auditory function. In order to investigate the relationship between categorical perception and dyslexia, as well as the nature of this categorization deficit, speech specific or not, the discrimination responses of children who have dyslexia and those of average readers to sinewave analogues of speech sounds were compared. These analogues were presented in two different conditions, either as nonspeech whistles or as speech sounds. Results showed that children with dyslexia are less categorical than average readers in the speech condition, mainly because they are better at discriminating acoustic differences between stimuli belonging to the same category. In the nonspeech condition, discrimination was also better for children with dyslexia, but differences in categorical perception were less clear-cut. Further, the location of the categorical boundary on the stimulus continuum differed between speech and nonspeech conditions. As a whole, this study shows that categorical deficit in children with dyslexia results primarily from an increased perceptibility of within-category differences and that it has a speech-specific component. These findings may have profound implications for learning and re-education.     

Children's perception of time-compressed speech on two measures of speech discrimination.

Time-compressed versions of the WIPI and PB-K 50 speech discrimination measures were presented at two sensation levels to 60 children divided into three age-groups of 20 each. Results showed that average intelligibility scores increased as a function of increasing age and sensation level and decreased with increasing amounts of time compression. The PB-K 50 measure was found to be more difficult than the WIPI for each age-group under each condition of time compression and sensation level. The several factors under study were found to interact. The results are discussed relative to open- versus closed-message set response tasks and the implications for audiological diagnoses of children with central auditory processing problems.     

Stimulus ratio effects on speech discrimination by children and adults

This investigation examined the response strategies and discrimination accuracy of adults and children aged 5-10 as the ratio of same to different trials was varied across three conditions of a "change/no-change" discrimination task. The conditions varied as follows: (a) a ratio of one-third same to two-thirds different trials (33% same), (b) an equal ratio of same to different trials (50% same), and (c) a ratio of two-thirds same to one-third different trials (67% same). Stimuli were synthetic consonant-vowel syllables that changed along a place of articulation dimension by formant frequency transition. Results showed that all subjects changed their response strategies depending on the ratio of same-to-different trials. The most lax response pattern was observed for the 50% same condition, and the most conservative pattern was observed for the 67% same condition. Adult response patterns were most conservative across condition. Difference in discrimination accuracy as measured by P(C) were found, with the largest difference in the 5- to 6-year-old group and the smallest change in the adult group. These findings suggest that children's response strategies, like those of adults, can be manipulated by changing the ratio of same-to-different trials. Furthermore, interpretation of sensitivity measures must be referenced to task variables such as the ratio of same-to-different trials.     

Binaural and monaural speech discrimination under reverberation.

This study investigated the effects of reverberation upon the speech discrimination performance of 30 normally hearing subjects and 30 persons with bilateral sensorineural hearing loss. Following preliminary tests, the Modified Rhyme Test was administered monaurally and binaurally at reverberation times of 0, 1, 2 and 3 sec. All stimuli were administered under earphones. The lists and conditions were appropriately randomized and counterbalanced so that each subject heard a test list at each reverberation time (RT) monaurally and binaurally. The expected gain due to binaural summation of loudness was simulated in order to test the possibility that any binaural enhancement of intelligibility might be due to binaural loudness summation. For all conditions, the normally hearing subjects performed significantly better than the hearing-impaired group. However, in relative terms, the two groups were remarkably similar. Binaural scores were significantly higher than monaural scores at each RT for both groups (in spite of homophasic conditions). For both groups, monaural and binaural scores decreased with increasing RT. Monaural scores decreased at a significantly faster rate with RT than did the binaural scores (the binaural advantage, however, was larger for the normal group). Increasing the monaural presentation levels to simulate the binaural loudness gain did not result in higher scores. It was concluded that speech discrimination under reverberation is better binaurally than monaurally for both normally hearing and hearing-impaired persons. This is due, at least partly, to the ability of the binaural auditory system to squelch the effects of reverberation. A tentative model is suggested for the binaural squelch of reverberation. The current findings are compared with existing data; and suggestions are offered for clinical application.     

Audio-visual discrimination of speech*

Tests utilizing audio-visual presentations of speech may have more significance than has hitherto been recognized. Such tests appear to offer more reliable, more realistic and more reproducible measures of communication impairments than either auditory speech discrimination tests, or visual speech discrimination tests.     

Correlates of phonological awareness in preschoolers with speech sound disorders.

PURPOSE: The purpose of this study was to examine the relationships among variables that may contribute to poor phonological awareness (PA) skills in preschool-aged children with speech sound disorders (SSD). METHOD: Ninety-five 4- and 5-year-old children with SSD were assessed during the spring of their prekindergarten year. Linear structural equation modeling was used to compare the fit of 2 models of the possible relationships among PA, speech perception, articulation, receptive vocabulary, and emergent literacy skills. RESULTS: Half the children had significant difficulty with speech perception and PA despite demonstrating receptive language skills within or above the average range. The model that showed the best fit to the data indicated that speech perception is a pivotal variable that has a direct effect on PA and an indirect effect that is mediated by vocabulary skills. Articulation accuracy did not have a direct impact on PA. Emergent literacy skills were predicted by PA abilities. CONCLUSIONS: Children with SSD are at greatest risk of delayed PA skills if they have poor speech perception abilities and/or relatively poor receptive vocabulary skills. Children with SSD should receive assessments of their speech perception, receptive vocabulary, PA, and emergent literacy skills.     

Function of the acoustic reflex in discrimination of intense speech.

It is known that the middle ear acoustic reflex (AR) alters the transmission characteristics of the auditory system; however, disagreement exists on how these changes may influence the ears; transfer of speech stimuli. In this study, speech with and without a competing message was delivered at supra-AR levels to cat ears that demonstrated an active and a pharmaceutically inactivated middle ear reflex mechanism. Resulting cochlear potentials were tape recorded and subsequently presented to 18 human subjects with normal hearing. Findings suggest word and sentence discrimination is enhanced in the presence of a functioning AR, with implications for hearing aid use and stapedectomy procedure.     

Relationship between speech motor control and speech intelligibility in children with speech sound disorders

The current study was undertaken to investigate the impact of speech motor issues on the speech intelligibility of children with moderate to severe speech sound disorders (SSD) within the context of the PROMPT intervention approach. The word-level Children's Speech Intelligibility Measure (CSIM), the sentence-level Beginner's Intelligibility Test (BIT) and tests of speech motor control and articulation proficiency were administered to 12 children (3:11 to 6:7 years) before and after PROMPT therapy. PROMPT treatment was provided for 45 min twice a week for 8 weeks. Twenty-four naïve adult listeners aged 22–46 years judged the intelligibility of the words and sentences. For CSIM, each time a recorded word was played to the listeners they were asked to look at a list of 12 words (multiple-choice format) and circle the word while for BIT sentences, the listeners were asked to write down everything they heard. Words correctly circled (CSIM) or transcribed (BIT) were averaged across three naïve judges to calculate percentage speech intelligibility. Speech intelligibility at both the word and sentence level was significantly correlated with speech motor control, but not articulatory proficiency. Further, the severity of speech motor planning and sequencing issues may potentially be a limiting factor in connected speech intelligibility and highlights the need to target these issues early and directly in treatment.