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G P Nerbonne

Publications and source records attributed to G P Nerbonne.

9 recordsLinked to original sources
PubMed1996

Consonant confusions in amplitude-expanded speech.

The perceptual consequences of expanding the amplitude variations in speech were studied under conditions in which spectral information was obscured by signal correlated noise that had an envelope correlated with the speech envelope, but had a flat amplitude spectrum. The noise samples, created individually from 22 vowel-consonant-vowel nonsense words, were used as maskers of those words, with signal-to-noise ratios ranging from -15 to 0 dB. Amplitude expansion was by a factor of 3.0 in terms of decibels. In the first experiment, presentation level for speech peaks was 80 dB SPL. Consonant recognition performance for expanded speech by 50 listeners with normal hearing was as much as 30 percentage points poorer than for unexpanded speech and the types of errors were dramatically different, especially in the midrange of S-N ratios. In a second experiment presentation level was varied to determine whether reductions in consonant levels produced by expansion were responsible for the differences between conditions. Recognition performance for unexpanded speech at 40 dB SPL was nearly equivalent to that for expanded speech at 80 dB SPL. The error patterns obtained in these two conditions were different, suggesting that the differences between conditions in Experiment 1 were due largely to expanded amplitude envelopes rather than differences in audibility.

Humans↗
PubMed1996

Consonant recognition for spectrally degraded speech as a function of consonant-vowel intensity ratio.

Normal-hearing subjects' recognition of spectrally degraded speech was evaluated under conditions in which the consonant-vowel (C-V) intensity ratio was modified. Subjects identified 22 consonants presented in an /a-Consonant-a/ format at suprathreshold and near threshold conditions. Prior to C-V ratio modification, the stimuli were processed to limit spectral information. In the suprathreshold experiment, stimuli were presented at the natural C-V ratio and at six modified C-V ratios. C-V ratio manipulations had dramatic effects on recognition scores for some groups of consonants. Scores for glides and sibilant fricatives increased with increasing C-V ratio, while scores for nasals and weak fricatives were best at low C-V ratios. Recognition scores for the stops and affricates were generally independent of C-V ratio. For nearly all consonants, changes in recognition scores as a function of C-V ratio were associated with changes in a general response bias toward those sounds. Performance was poor when the spectrally smeared VCVs were presented at low SN ratios in a second experiment. The influence of C-V ratio on percent correct scores was generally similar to the suprathreshold results, but consonant audibility, which was not a factor in the suprathreshold experiment, appeared to alter the effect of C-V ratio modification for some consonants.

Humans↗
PubMed1991

Effect of consonant-vowel ratio modification on amplitude envelope cues for consonant recognition.

This investigation examined the degree to which modification of the consonant-vowel (C-V) intensity ratio affected consonant recognition under conditions in which listeners were forced to rely more heavily on waveform envelope cues than on spectral cues. The stimuli were 22 vowel-consonant-vowel utterances, which had been mixed at six different signal-to-noise ratios with white noise that had been modulated by the speech waveform envelope. The resulting waveforms preserved the gross speech envelope shape, but spectral cues were limited by the white-noise masking. In a second stimulus set, the consonant portion of each utterance was amplified by 10 dB. Sixteen subjects with normal hearing listened to the unmodified stimuli, and 16 listened to the amplified-consonant stimuli. Recognition performance was reduced in the amplified-consonant condition for some consonants, presumably because waveform envelope cues had been distorted. However, for other consonants, especially the voiced stops, consonant amplification improved recognition. Patterns of errors were altered for several consonant groups, including some that showed only small changes in recognition scores. The results indicate that when spectral cues are compromised, nonlinear amplification can alter waveform envelope cues for consonant recognition.

Adolescent↗
PubMed1989

The importance of consonant-vowel intensity ratio in the intelligibility of voiceless consonants.

The purpose of this study was to evaluate the extent to which variations in the consonant-vowel (C-V) intensity ratio could account for variations in speech intelligibility among the productions of 10 talkers. Fifty normal-hearing individuals listened in noise to syllables consisting of voiceless consonants followed by the vowel /a/ under three conditions in which: (a) C-V ratio varied naturally as produced by the talkers, and the stimuli were calibrated according to vowel intensity; (b) C-V ratios were increased and equated via digital signal processing; and (c) C-V ratios were unmodified, but the syllables were calibrated according to consonant level rather than vowel level. Results indicated that variations in C-V ratio explained a great deal of the variation in the intelligibility of some consonants (/s, S, tS/) but not others (the voiceless stops). This difference may well be due to differences in audibility between the two groups of consonants when they are presented at similar consonant-to-noise ratios. The majority of the data suggest that the importance of C-V ratio is related to the intensity of consonants but is independent of the ratio per se between consonant and vowel levels.

Adult↗
PubMed1987

Measuring helmet sound attenuation characteristics using an acoustic manikin.

The sound attenuation characteristics of two military helmets were measured using an acoustic manikin as the test apparatus. The manikin results are compared to the results of attenuation measurements made on human subjects wearing identical helmets. The testing room and instrumentation were the same for both the manikin and human subjects. Procedures in ANSI S3.19-1974 were used in the real-ear attentuation at threshold (REAT) part of this study. The results are encouraging as they suggest that the manikin may be used in place of a panel of human subjects to evaluate the hearing protection characteristics of military head gear.

Acoustics↗
PubMed1978

Environmental noise in a residential institution for mentally retarded persons.

The present study was designed to survey the noise characteristics in residence halls housing young mentally retarded children and test the effects of this noise on speech-discrimination performance of the residents. The noise survey indicated that the mean level of the noise was 75 dB SPL (WIth the level greater than 70 dB SPL during 71 percent of the sampling time). The spectrum was similar in configuration to the long-time speech spectrum. Selected residents were tested for speech discrimination in quiet and noise conditions. Mean scores on the Word Intelligibility by Perception Identification test were 73.9 percent correct in the quiet and 44 percent correct in the noise conditions. We concluded that the residents, who already had a primary language-learning handicap, were being subjected to a possible secondary impediment resulting from their living environment.

Adolescent↗