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Biomedical subjects

A Boothroyd

Publications and source records attributed to A Boothroyd.

At least 37 records · Page 2Linked to original sources
PubMed1996

Using naturally produced speech to elicit the mismatch negativity.

The mismatch negativity (MMN) was recorded from 10 young adults with normal hearing using naturally produced speech contrasts. Consonant-place and vowel-height contrasts were examined in consonant-vowel (CV) syllables by pairing either the consonant /t/ or /p/ with the vowel /I/ or /E/. Vowel-height was also examined as a pseudovowel; one cycle of the vowel segment of a CV was extracted and replicated over 200 msec. A total of five contrasts were examined: vowel-height following /p/, vowel-height following /t/, consonant-place preceding /E/, consonant-place preceding /I/, and pseudovowels. Significant MMN responses were elicited from all five contrasts, albeit with different amplitudes, latencies, and waveform morphology. The pseudovowel elicited the most well-defined MMN with the greatest amplitude and was found to be significantly different from the other four contrasts. Naturally produced speech stimuli appear to be viable stimuli for eliciting the MMN.

Adult↗
PubMed1996

Speech perception of temporally reversed syllables by normally hearing adults.

BACKGROUND: The general purpose of this study was to determine the effects of phonological knowledge on performance on a simple task of speech discrimination. If a test can be devised that is independent of the subject's phonological knowledge then it should be possible to measure auditory speech perception capacity in young deaf children before they have developed spoken language skills. In the present study, temporal reversal was used to limit normal subjects' use of phonological knowledge without removing acoustic information. METHODS: An auditory, 3-interval, forced-choice (oddity) test of phonetic contrast perception was administered to 5 normally hearing adult speakers of English. Perception of place of articulation was measured in stops and fricatives--both voiced and unvoiced. The test was presented both with natural syllables and with the same syllables reversed in time. In addition, the test was administered with a fixed context and a mixed context (i.e., context changing from trial to trial). The subject's task was always to identify the odd-man-out in each presentation of 3 syllables. RESULTS: Overall, error rate was significantly higher for temporally-reversed than for natural syllables (6.7% versus 1.7%). The effect was, however, present only in stops (11.7% versus 1.7%) and not in fricatives (0.8% versus 0.8%). Changing from a fixed to a mixed context did not influence the effect of reversal. There were, however, significant differences among subjects in the temporally-reversed condition. CONCLUSIONS: The main effect of reversal supports the hypothesis that performance falls, even on a simple task, when phonetic processing is impeded. The fact that the effect is present only for stops adds further support, because temporal reversal does not affect the essential acoustic properties of fricatives. The presence of inter-subject differences suggests that the ability to switch to an acoustic strategy when phonetic processing is impeded may be affected by aptitude and experience. The fact that error rate was low, even for reversed stops, suggests that a test of this type could be used for assessing speech perception capacity in deaf children with impaired phonology. The procedure is not, however, completely independent of the effects of phonetic processing.

Adult↗
PubMed1995

Speechreading supplemented by single-channel and multichannel tactile displays of voice fundamental frequency.

The benefits of two tactile codes of voice fundamental frequency (F0) were evaluated as supplements to the speechreading of sentences in two short-term training studies, each using 12 adults with normal hearing. In Experiment 1, a multichannel spatiotemporal display of F0, known as Portapitch, was used to stimulate the index finger. In an attempt to improve on past performance with this display, the coding scheme was modified to better cover the F0 range of the talker in the training materials. For Experiment 2, to engage kinesthetic/proprioceptive pathways, a novel single-channel positional display was built, in which F0 was coded as the vertical displacement of a small finger-rest. Input to both displays consisted of synthesized replicas of the F0 contours of the sentences, prepared and perfected off-line. Training with the two tactile F0 displays included auditory presentation of the synthesized F0 contours in conjunction with the tactile patterns on alternate trials. Speechreading enhancement by the two tactile F0 displays was compared to the enhancement provided when auditory F0 information was available in conjunction with the tactile patterns, by auditory presentation of a sinusoidal indication of the presence or absence of voicing, and by a single-channel tactile display of the speech waveform presented to the index finger. Despite the modified coding strategy, the multichannel Portapitch provided a mean tactile speechreading enhancement of 7 percentage points, which was no greater than that found in previous studies. The novel positional F0 display provided only a 4 percentage point enhancement. Neither F0 display was better than the simple single-channel tactile transform of the full speech waveform, which gave a 7 percentage point enhancement effect. Auditory speechreading enhancement effects were 17 percentage points with the voicing indicator and approximately 35 percentage points when the auditory F0 contour was provided in conjunction with the tactile displays. The findings are consistent with the hypothesis that subjects were not taking full advantage of the F0 variation information available in the outputs of the two experimental tactile displays.

Adult↗
PubMed1995

Comparison of two multichannel tactile devices as supplements to speechreading in a postlingually deafened adult.

OBJECTIVE: The purpose of this study was to conduct a single-subject comparison of the effectiveness of two multichannel vibrotactile devices that encode different classes of speech information. One device, the Portapitch, is designed to convey fundamental frequency (F0) and its variation over time. The other, the TACTAID 7, is designed to convey the first two formant frequencies (F1 and F2) and their variation over time. DESIGN: The subject, a postlingually deafened adult, underwent an intensive 17-wk training and testing protocol with the Portapitch and then completed a similar 17-wk protocol with the TACTAID 7. Performance measures were obtained on phonetic-contrast perception by speechreading alone, tactile device alone, and speechreading plus tactile device, and on open-set word and sentence recognition by speechreading alone and speechreading plus tactile device. RESULTS: On phonetic-contrast testing, the subject demonstrated some ability to perceive voicing, stress, and intonation contrasts using the Portapitch, but gave little evidence of phonetic-contrast perception with the TACTAID 7. On open-set word recognition testing, no significant improvements were seen with either device. On open-set sentence recognition testing, the subject showed a significant 9 percentage point enhancement effect using the Portapitch; the mean 5 percentage point enhancement effect provided by the TACTAID 7 was not statistically significant. CONCLUSIONS: A small advantage was seen in favor of the tactile display of F0 relative to the tactile display of formant frequency information on both phonetic-contrast testing and open-set sentence recognition. The difference, however, was of questionable significance and could have been confounded with an order effect. Nevertheless, the subject's preference was for the tactile formant frequency display.

Adult↗
PubMed1995

Ultrasound: a helpful guide in the treatment of congenital talipes equinovarus.

Ultrasound may be used to distinguish the unossified cartilage and the ossification centres of the tarsal bones. The use of ultrasound to image the normal foot and the foot with congenital talipes equinovarus (CTEV) deformity has been assessed. We describe two standard ultrasound planes that enable the normal foot to be distinguished from the foot with a CTEV deformity even before it becomes clinically apparent. The technique does not take much time, is easily tolerated by the child, and may be repeated frequently to assess the response to treatment. It can be learned easily.

Clubfoot↗
PubMed1994

Breast masses in childhood and adolescence. A presentation of 17 cases and a review of the literature.

Breast masses are uncommon in the first two decades of life. 17 girls aged between 2 and 15 years who presented over a 5-year period are reviewed retrospectively. The cases comprised inflammation (11), asymmetrical gynaecomastia (1), precocious puberty (1), giant juvenile fibroadenoma (1), primary rhabdomyosarcoma (1), lymphoma (1), and metastatic neuroblastoma (1). Ultrasound was useful in all cases in identifying the abnormality and guiding any further investigation.

Adolescent↗
PubMed1994

The hearing aid input: a phonemic approach to assessing the spectral distribution of speech.

OBJECTIVES: The long-term goal is to investigate the feasibility of using real speech as a stimulus for electroacoustic evaluation of nonlinear hearing aids. The goals of the present study were to determine the spectral envelope of speech from acoustic measures of phoneme tokens in running speech, to compare the results with published data on long-term average speech spectra, to measure inter-talker differences of spectral envelope, and to explore the extent to which the intensity variation within and across talkers might be minimized by frequency-selective amplification and automatic gain control. DESIGN: Seven phonemes were selected to represent the extremes of frequency and intensity in English. Recordings were made of five men and five women producing syllable strings constructed from these phonemes. One-third octave spectra were prepared from the phoneme tokens. The frequencies and intensities of 13 key points in these spectra were measured and used to estimate individual and group spectral envelopes. RESULTS: The group spectral envelope was similar to that derived from published data on the long-term average spectrum of speech, but there were marked intertalker differences. Some of the differences were gender-related. The overall dynamic range of intensity in these data was 53 dB. Frequency-dependent level adjustment (an 11 dB high-frequency boost) reduced this range to 42 dB, and a combination of frequency-dependent and subject-dependent level adjustment (analogous to 2-band automatic gain control) reduced it to 37 dB. CONCLUSION: A phonemic approach to determining the spectral envelope of speech offers insights that are not available from long-term average spectra and could offer advantages in the evaluation of nonlinear hearing aids.

Adult↗
PubMed1993

Recovery of speech perception performance after prolonged auditory deprivation: case study.

The case reported here, a 26-year-old woman, has a bilaterally symmetric, severe-to-profound, sensorineural hearing loss, acquired early in life. Phoneme recognition scores were essentially symmetric at the onset of the investigation. She was basically monaurally aided from age 4 to age 24, at which time a loss of function in the aided ear prompted the change to binaural amplification. When monaurally aided, this subject had consistently given phoneme recognition scores around 80 percent and 40 percent in the aided and unaided ears, respectively, even though the pure-tone thresholds were almost identical. After several months of hearing aid use, phoneme recognition in the previously unaided ear rose to 75 percent. At the time of writing, this subject is able to hold unstructured telephone conversations via this ear. These data suggest that the earlier poor performance of the unaided ear was due, not to an irreversible loss of peripheral function, but to a lack of experience in interpreting the patterns of neural stimulation generated by that ear.

Acoustic Stimulation↗
PubMed1992

Speechreading enhancement by voice fundamental frequency: the effects of Fo contour distortions.

Recognition of words in sentences of known topic was measured in normally hearing adults via speechreading alone and speechreading supplemented with auditory presentation of signals intended to convey variations of voice fundamental frequency (Fo) over time. Three signals were used: (a) the low-pass filtered output of an electroglottograph (unprocessed Fo), (b) a constant amplitude sine wave whose instantaneous frequency was intended to equal that of Fo (processed Fo), and (c) the same sine wave restricted to a small number of discrete frequency steps (quantized Fo). As the number of steps in the quantized Fo contours increased from 1 to 12, the speechreading enhancement effect increased. The quantized Fo contour with 12 steps was as effective as the processed Fo contour (without quantization), but this processed contour was significantly less effective than the unprocessed electroglottograph signal. The results show that the auditory Fo speechreading enhancement effect is sensitive to the errors introduced by the Fo extraction and regeneration process used in this study. It is also sensitive to the quantization of Fo contours into less than 12 steps. Whether more than 12 steps are required for the full enhancement effect remains to be determined.

Adult↗
PubMed1992

Spectral distribution of /s/ and the frequency response of hearing aids.

The purpose was to determine a target for the upper frequency limit of a hearing aid that will provide access to the important spectral cues for all the sounds of English. The sibilant /s/ was studied because of its high-frequency content. Repeated tokens of /s/ were recorded from five men and five women before and between the vowels /u/, /a/, and /i/. Using fast Fourier transform analysis, the prominent spectral peak with the lowest frequency was identified and its center frequency determined for each token. This frequency averaged around 4.9 kHz for the /u/ context, 5.6 kHz for the /a/ context, and 6.0 kHz for the /i/ context. There were dramatic differences among talkers, with subject means ranging from 3.2 to 8.4 kHz. The women generated consistently higher frequency /s/ sounds than the men, but there were also large differences within gender groups. These data suggest that the upper frequency limit of a high-fidelity hearing aid should be in the region of 10 kHz. If this cannot be accomplished with direct amplification, an alternative might be the selective use of frequency transposition.

Adult↗
PubMed1992

Effects of noise and noise suppression on speech perception by cochlear implant users.

The recognition of phonemes in consonant-vowel-consonant words, presented in speech-shaped random noise, was measured as a function of signal to noise ratio (S/N) in 10 normally hearing adults and 10 successful adult users of the Nucleus cochlear implant. Optimal scores (measured at a S/N of +25 dB) were 98% for the average normal subject and 42% for the average implantee. Phoneme recognition threshold was defined as the S/N at which the phoneme recognition score fell to 50% of its optimal value. This threshold was -2 dB for the average normal subject and +9 dB for the average implantee. Application of a digital noise suppression algorithm (INTEL) to the mixed speech plus noise signal had no effect on the optimal phoneme recognition score of either group or on the phoneme recognition threshold of the normal group. It did, however, improve the phoneme recognition threshold of the implant group by an average of 4 to 5 dB. These findings illustrate the noise susceptibility of Nucleus cochlear implant users and suggest that single-channel digital noise reduction techniques may offer some relief from this problem.

Adult↗
PubMed1991

Relations between prosodic variables and communicative functions.

Three children were observed interacting with their mothers at three different times: before the onset of single words, when vocabulary consisted of 10 words, and when vocabulary consisted of 50 words. Relations between communicative functions and acoustic analyses of prosodic variables (i.e. rise vs. nonrise of terminal contours) were studied. Considerable variability was found among the children in the number of rises produced overall and those produced for any function. Each child's use of rise was fairly constant over time and rises were produced relatively more frequently than nonrises with functions requiring a response from the listener. Factors affecting similarities and differences are discussed.

Child Language↗
PubMed1991

Assessment of speech perception capacity in profoundly deaf children.

This paper describes an approach to speech perception testing that involves assessment of the probability of perception of phonologically significant speech pattern contrasts presented in a varying phonetic context. Such an approach provides analytic detail about a subject's access to sensory data, with minimal influence from linguistic context. Nevertheless, the results are predictive of performance at the level of conversation. For use with young children, the approach has been incorporated into a three-interval oddity test and an imitative test. Additional options under investigation include a video-game, psychoacoustic testing, and electrophysiologic testing.

Child↗
PubMed1990

Context effects in phoneme and word recognition by young children and older adults.

Perception is influenced both by characteristics of the stimulus, and by the context in which it is presented. The relative contributions of each of these factors depend, to some extent, on perceiver characteristics. The contributions of word and sentence context to the perception of phonemes within words and words within sentences, respectively, have been well studied for normal, young adults. However, far less is known about these context effects for much younger and older listeners. In the present study, measures of these context effects were obtained from young children (ages 4 years 6 months to 6 years 6 months) and from older adults (over 62 years), and compared with those of the young adults in an earlier study [A. Boothroyd and S. Nittrouer, J. Acoust. Soc. Am. 84, 101-114 (1988)]. Both children and older adults demonstrated poorer overall recognition scores than did young adults. However, responses of children and older adults demonstrated similar context effects, with two exceptions: Children used the semantic constraints of sentences to a lesser extent than did young or older adults, and older adults used lexical constraints to a greater extent than either of the other two groups.

Aged↗
PubMed1988

Amplitude compression and profound hearing loss.

Nine subjects with prelingually acquired, sensorineural, hearing loss were given a three-interval, forced-choice, test of speech pattern contrast perception under two amplification conditions. The first involved adjustment of the low and high frequency outputs of a two-channel Master Hearing Aid to each subject's highest comfortable level, but without compression of the short-term dynamic range of the signal. The second involved the additional compression of a 30 dB input range into the subject's dynamic range of hearing, as measured by the difference between speech awareness threshold and highest comfortable level, in each of the two channels. One of the subjects performed much better with compression than without. Among the other eight, however, there was a small but significant reduction of performance when compression was introduced. It is proposed that the one positive result is due to the increased audibility of speech cues made possible by amplitude compression. It is further proposed that the negative results are due mainly to the distortions of time-intensity cues introduced by amplitude compression. The results suggest that, in terms of potential access to meaningful speech cues, the addition of amplitude compression, to an otherwise optimized signal, is unnecessary, or even detrimental, for most profoundly deaf subjects, but could be beneficial for some.

Adolescent↗
PubMed1988

Voice fundamental frequency as an auditory supplement to the speechreading of sentences.

Recognition of words in conversational sentences of known topic was measured in nine normally hearing subjects by speechreading alone and by speechreading supplemented with auditory presentation of the output of an electroglottograph. Mean word recognition probability rose from 30% to 77% with the addition of the acoustic signal. When this signal was filtered to remove possible high-frequency spectral cues, the supplemented score fell, but only by a marginally significant 7 percentage points, supporting the conclusion that voice fundamental frequency was the principal source of enhancement. Enhancement occurred for all subjects, regardless of speechreading competence.

Communication Devices for People with Disabilities↗