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A Boothroyd

Publications and source records attributed to A Boothroyd.

At least 19 recordsLinked to original sources
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↗
PubMed1988

Perception of speech pattern contrasts from auditory presentation of voice fundamental frequency.

The perception of phonologically significant speech pattern contrasts was measured in normally hearing subjects who were presented with F0 contours alone, speechreading alone, and the two in combination. For the suprasegmentals and final consonant voicing, perception in the combined condition was dominated by F0. For the vowel, consonant place, and final consonant continuance contrasts, perception in the combined condition was dominated by vision. For initial consonant voicing and continuance, however, there was clear evidence of interaction between F0 and speechreading. Here, the combined score was higher than either of the single-modality scores, and also higher than could be predicted on the assumption that the auditory and visual channels act as statistically independent channels of information.

Adult↗
PubMed1988

Tactile presentation of voice fundamental frequency as an aid to the speechreading of sentences.

In two experiments, the perception of words in sentences was measured by speechreading with and without tactile presentation of voice fundamental frequency (F0). The first experiment involved normally hearing subjects and two kinds of tactile display of F0: (1) a spatial, multichannel display; and (2) a temporal, single-channel display. Mean performance with the tactile displays was found to be slightly, but significantly, better than speechreading alone, but no significant difference was found between the two displays. The second experiment involved hearing-impaired subjects and only the spatial, multi-channel display of F0. For all three subjects, after extended training, speechreading performance was significantly better with the addition of the tactile display than by speechreading alone. The improvement amounted to reductions of word recognition error of 24, 33, and 50% in the three subjects.

Adult↗
PubMed1988

A wearable multichannel tactile display of voice fundamental frequency.

This paper describes a wearable sensory aid that provides the deaf with tactually encoded information about intonation. Fundamental frequency is represented as both place and rate of vibration in a linear array of solenoids. Pitch extraction is accomplished through low-pass filtering and peak detection. A microcomputer is used to measure pitch period, which in turn determines which of the solenoids is actuated. By comparing consecutive periods, the system discriminates against random, noise-related inputs. The device is switchable between 1-, 8-, and 16-channel operation. The electronics package is contained in a case that may be worn on a belt. The solenoid array is worn on the forearm. The system is powered by five, rechargeable lithium cells and runs for at least 6 hours between charges. Proposed developments include the incorporation of digital pitch extraction methods and the option to use the spatial output dimension to encode speech parameters other than fundamental frequency.

Deafness↗
PubMed1988

Mathematical treatment of context effects in phoneme and word recognition.

Percent recognition of phonemes and whole syllables, measured in both consonant-vowel-consonant (CVC) words and CVC nonsense syllables, is reported for normal young adults listening at four signal-to-noise (S/N) ratios. Similar data are reported for the recognition of words and whole sentences in three types of sentence: high predictability (HP) sentences, with both semantic and syntactic constraints; low predictability (LP) sentences, with primarily syntactic constraints; and zero predictability (ZP) sentences, with neither semantic nor syntactic constraints. The probability of recognition of speech units in context (pc) is shown to be related to the probability of recognition without context (pi) by the equation pc = 1 - (1-pi)k, where k is a constant. The factor k is interpreted as the amount by which the channels of statistically independent information are effectively multiplied when contextual constraints are added. Empirical values of k are approximately 1.3 and 2.7 for word and sentence context, respectively. In a second analysis, the probability of recognition of wholes (pw) is shown to be related to the probability of recognition of the constituent parts (pp) by the equation pw = pjp, where j represents the effective number of statistically independent parts within a whole. The empirically determined mean values of j for nonsense materials are not significantly different from the number of parts in a whole, as predicted by the underlying theory. In CVC words, the value of j is constant at approximately 2.5. In the four-word HP sentences, it falls from approximately 2.5 to approximately 1.6 as the inherent recognition probability for words falls from 100% to 0%, demonstrating an increasing tendency to perceive HP sentences either as wholes, or not at all, as S/N ratio deteriorates.

Adult↗
PubMed1988

Spatial, tactile presentation of voice fundamental frequency as a supplement to lipreading: results of extended training with a single subject.

An adult with a severe, postlingually-acquired, sensorineural, hearing loss was given 2 hours a week of training in the perception of connected discourse by lipreading, supplemented by voice fundamental frequency (Fo), encoded as locus of vibratory stimulation of the forearm. Three, 3-week blocks of training in the supplemented condition were interspersed with 1-week periods of training by lipreading alone. Training was conducted via a computer-controlled, interactive video system, using a semi-automated connected discourse tracking procedure. Performance was measured as the percentage of words correctly recognized on the first presentation of new sentence material. Scores by lipreading alone averaged approximately 65 percent and remained essentially constant over the 13 weeks of training. Scores under the supplemented condition rose from 65 percent at the beginning of the study to 85 percent at the end. The final supplemented score represented roughly a 50 percent reduction of error rate, when compared with lipreading alone. Performance with the tactile supplement was not as good as with auditorily presented Fo, but was better than has previously been reported in the literature. These data provide evidence to support the notion that subjects can learn to integrate novel tactile codes with the visual stimulus during the lipreading of connected speech.

Adult↗
PubMed1987

Effect of two approaches to auditory training on speech recognition by hearing-impaired adults.

Twenty adults with mild to moderate sensorineural hearing impairments were given three tests of speech recognition: the CUNY Nonsense Syllable Test (NST), the low predictability items of the Revised Speech Perception in Noise (RSPIN) test, and the high predictability items of the RSPIN test. They were tested on four occasions: at the beginning of the study, after one month of "no treatment," after a month of intensive auditory training, and after a further month of "no treatment." During the treatment period, 10 of the subjects spent all of the time on activities involving sentence perception and perceptual strategy while the other 10 spent half of the time on activities involving consonant recognition. A small, but statistically significant increase in speech recognition performance on the high probability material was observed in both groups subsequent to training, but the effect of training method was not significant. In addition, the gains achieved were not lost in the month following the end of training. The findings suggest that the benefits of auditory training were found in an increased use of sentence context as an aid to word recognition.

Aged↗