J. M. Pickett

Acoustic cues to final stop voicing for impaired‐ and normal‐hearing listeners

Voicing perception for final stops was studied for impaired- and for normal-hearing listeners when cues in naturally spoken syllables were progressively neutralized. The syllables were ten different utterances of /daep, daek, daet, daeb, daeg, daed/ spoken in random order by a male. The cue modifications consisted progressively of neutralized vowel duration, equalized occlusion duration, burst deletion, murmur deletion, vowel-transition interchange, and transition deletion. The impaired subjects had moderate-to-severe losses and showed at least 70% correct voicing for the unmodified syllables. For the voiced stops, vowel-duration adjustment and murmur deletion each resulted in significant reductions in voicing perception for more than one-third of the impaired listeners; all normals showed good performance following neutralization of these cues. For the voiceless stops, large percentages of both listener groups showed decreased voicing perception due to the burst deletion, though a majority of both groups performed well above change even after the vowel-duration adjustment and the burst deletion. When the vowel off-going transitions were exchanged between cognate syllables in given pairs, the effect on voicing perception exhibited by many impaired- and all normal-hearing listeners implicated the vowel transitions as an important additional source of cues to final-stop voicing perception.

Recent research on speech-analyzing aids for the deaf

The problem of acoustic transmission of speech sounds to the deaf is reviewed. Then some methods of speech analysis are described which have been developed as prototypes of new speech aids. Three types of new aids are covered: 1) aids intended for improving speech reception by recoding or transposing speech sounds into residual hearing ranges, 2) tactual aids to speech communication, and 3) visual aids to supplement speech reception, or for monitoring of speech in speech training.

Perceptual cues to the voiced–voiceless distinction of final fricatives for listeners with impaired or with normal hearing

Cues to the voicing distinction for final /f,s,v,z/ were assessed for 24 impaired- and 11 normal-hearing listeners. In base-line tests the listeners identified the consonants in recorded /d circumflex C/ syllables. To assess the importance of various cues, tests were conducted of the syllables altered by deletion and/or temporal adjustment of segments containing acoustic patterns related to the voicing distinction for the fricatives. The results showed that decreasing the duration of /circumflex/ preceding /v/ or /z/, and lengthening the /circumflex/ preceding /f/ or /s/, considerably reduced the correctness of voicing perception for the hearing-impaired group, while showing no effect for the normal-hearing group. For the normals, voicing perception deteriorated for /f/ and /s/ when the frications were deleted from the syllables, and for /v/ and /z/ when the vowel offsets were removed from the syllables with duration-adjusted vowels and deleted frications. We conclude that some hearing-impaired listeners rely to a greater extent on vowel duration as a voicing cue than do normal-hearing listeners.

VCVs vs CVCs for stop/fricative distinctions by hearing‐impaired and normal‐hearing listeners

Moderately to profoundly hearing-impaired (n = 30) and normal-hearing (n = 6) listeners identified [p, k, t, f, theta, s] in [symbol; see text], and [symbol; see text]s tokens extracted from spoken sentences. The [symbol; see text]s were also identified in the sentences. The hearing-impaired group distinguished stop/fricative manner more poorly for [symbol; see text] in sentences than when extracted. Further, the groups performance for extracted [symbol; see text] was poorer than for extracted [symbol; see text] and [symbol; see text]. For the normal-hearing group, consonant identification was similar among the syllable and sentence contexts.

Some applications of speech analysis to communication aids for the deaf

The problem of acoustic transmission of speech sounds to the deaf is discussed along with the related educational problems. Some methods of speech analysis which have been developed as prototypes of new speech aids are presented. Two types of new aids are covered: 1) tactual aids to speech communication, and 2) visual aids for monitoring of speech in speech training or to supplement speech reception.

Status of speech-analyzing communication aids for the deaf

Recent developments of prototype speech-processing aids intended to present speech information to persons with severe losses of hearing are summarized. The major types of devices are described, including those for speech reception and for speech training, and those that employ displays that are visual, factual, or auditory.

Discrimination of Vowel Spectrum in Sensorineural Hearing Impairment

Measurements are reported comparing normal and impaired auditory discrimination for formant frequencies of synthetic vowels. Vowel spectra were shaped by two formant resonators with controllable center frequencies, F1 and F2. For discrimination measurements three vowels were presented on each trial. For two of the vowels, F1 and F2 were held constant. For the third vowel, F2 was set at a higher frequency. The task of the listener was to tell which one of the vowels was different from the other two. A programmer controlled the synthesizer so as to present a sequence of trials with downward adjustment of amount of F2 difference after each correct response and upward adjustment after each wrong response. Thus, over a sequence of trials the amount of F2 difference typically decreased from above the difference limen until oscillatory adjustments occurred above and below the limen. Results: frequency position and relative amplitude of F1 has a marked effect of the F2 discrimination limen. All groups show good F...

The effects of duration adjustments of preceding vowels on fricative voicing perception by hearing‐impaired listeners

For /baef/, /baev/, /baes/, and /baez/, perception of the fricative voicing distinction was studied for 25 moderately to profoundly hearing‐impaired undergraduates. The purpose was to discover whether some listeners might benefit from enhancement of the duration cue in the preceding vowel. Identification was tested for ten utterances of each syllable. These utterances were presented unedited or with their vowels adjusted for duration. The utterances of /baef/ versus /baev/ and /baes/ versus /baez/ had been selected to differ in the degree of contrast for the vowel duration cue. The unedited utterances best‐perceived for fricative voicing contained vowels that were the most salient for the duration cue. The durations of these vowels were exemplars to be approximated among the other utterances that were adjusted for vowel duration. For /baef/, and /baes/ utterances, the vowels were shortened through pitch‐period deletions; the adjusted /baev/ and /baez/ utterances contained vowels lengthened via iterated pitch periods. Preliminary analyses revealed that the utterances with duration‐adjusted vowels yielded substantially improved fricative voicing perception for 15 of the listeners. The other listeners showed minimal changes in performance between the unedited versus vowel‐adjusted syllables. These were listeners whose perception for the unedited syllables was either very good or very poor.

Upward Spread of Masking in Normal and Sensorineural Subjects

In recent years, hearing aids and auditory‐training units have been introduced that attempt to present speech information in the low frequencies. The present study is an initial step in the investigation of upward‐spread‐of‐masking effects on discrimination in the middle and high frequencies. The purpose was to study the effect of a low‐frequency masker on the threshold of hearing at higher frequencies. The masker was a 250‐Hz low‐pass noise presented at over‐all levels of 77, 97, or 107 dB SPL. Pure‐tone thresholds were obtained at 200, 300, 500, 1000, and 2000 Hz. Normal‐hearing subjects and 27 subjects with sensorineural losses were tested. Results: Sensorineural subjects, as a group, do not demonstrate a “typical” pattern of masking. Within groups of subjects having similar losses, marked differences in upward spread of masking are found: Some subjects show less‐than‐normal masking; others, the same as normal. Subjects with moderately severe losses show higher masked thresholds than do subjects with m...

Impaired‐ and normal‐hearing listeners’ recognition of [b, d, g, v, z, edh] in [ΛCΛ] isolated versus in sentence contexts.

Recognition of consonants in connected speech has received limited study for severely hearing‐impaired listeners. Such listeners were tested (n=7) for identification of [b, d, g, v, z, edh] in [ΛCΛ] tokens, each embedded in a spoken carrier sentence (male talker) and extracted from the sentences. The severely hearing‐impaired listeners’ recognition was poorer for the consonants in the [ΛCΛ]’s when in the sentence context than when extracted. In contrast, neither a group of moderately impaired (n=11) nor of normal‐hearing listeners (n=6) showed a significant effect of context on consonant recognition. Performance by the severely hearing‐impaired listeners was not improved by insertion of an artificial pause preceding the word containing the test consonant in the sentence.