S. Revoile

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.

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.

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.

Perception of initial glides by impaired‐ or normal‐hearing listeners

An experiment was conducted to study the use of cues to glide consonant identification by hearing‐impaired (n = 22) and normal‐hearing (n = 6) listeners. The syllables /waek, jaek, baek, daek, gaek, aek/ (six different utterances each) were identified for three conditions: (1) unmodified, (2) initial glide murmurs or stop bursts removed, and (3) syllables cut back to the ninth pitch period from the vowel onset. The normal group, listening at 75 or 95 dB SPL, showed 100% glide phoneme perception for the condition of deleted glide murmurs or stop bursts. For this condition performances varied greatly within the hearing‐imparied group (listening at MCL): Near‐normal glide phoneme perception was seen for less than 20% of the impaired listeners (mean 3FA = 72 dB HL), indicating good use of the vowel onset transitions for glide perception by these listeners. Between the conditions: Unmodified versus glide‐murmur/stop‐bursts deleted, the majority of the hearing‐impaired listeners (mean 3FA = 88 dB HL) manifested degra...

Initial stop burst place perception for normal‐ and impaired‐hearing listeners

This study examined whether hearing‐impaired listeners could identify place of articulation for initial stop consonants, using information occurring early in the stop release; for normal‐hearing listeners this release information has been implicated as a highly important cue for place perception of initial stops. Place perception for the release bursts of initial stop consonants was tested for impaired‐(N = 23) and for normal‐hearing (N = 6) listeners. The burst were obtained from ten utterances each of the syllables /pad/, /kad/, /tad/, /bad/, /gad/, /dad/. Three test conditions were used: (1) the entire syllable; (2) the initial release transients alone; and (3) the aspirations following the transients of the voiceless consonants. For the normal‐hearing group, consonant perception was 100% when tested for the entire syllable; consonant place perception for the transients only, was 87%, and for the voiceless aspirations 67%. Among the hearing‐impaired listeners, mean stop place perception was about 60% w...

Impaired‐ and normal‐hearing listeners' voicing perception of final fricatives in cue‐adjusted syllables

In the spoken syllables /d∧z/ versus /d∧s/ and /d∧v/ versus /d∧f/, vowel duration differences were reduced, frications deleted, and vowel offsets exchanged or deleted. These adjustments were performed digitally on ten different tokens of each syllable. The voicing cues were adjusted in various combinations to yield different test conditions for identification of the syllables. Hearing‐impaired (N = 24) and normal‐hearing (N = 11) listeners were tested several times under each condition. For both listener groups, fricative voicing perception was generally unaffected by deletion of the frications from the syllables. The vowel duration adjustments (lengthening vowels that preceded voiceless frication, shortening vowels preceding voiced) significantly reduced fricative voicing perception for about half of the hearing‐impaired listeners; none of the normal‐hearing listeners was significantly affected by the vowel duration adjustment. When the vowel offsets (final seven pitch periods) were exchanged between voi...

Burst, murmur, vowel duration, and transition cues in the identification of final stop voicing by hearing‐impaired and normal‐hearing listeners

The effects on voicing identification of progressive neutralization of the voicing cues was examined further (99th ASA meeting, Paper GG6). Cue modifications were digital deletions or iterations performed on ten voicing‐cognate pairs of token syllables, spoken in a randomized list of 10× the set: dap, dak, dat, dab, dag, dad. The cue modifications consisted progressively of neutralized vowel durations, equalized closure duration, burst deletion, murmur deletion, and transition deletion. For voiced‐consonant syllables, about half of the 25 hearing‐impaired were sensitive to vowel duration and the presence of transitions; some of these listeners and others were sensitive to the presence of the burst and/or murmur. For syllables with unvoiced consonants, vowel duration and the presence of release burst affected identification for about half of the hearing impaired. Among the remaining impaired listeners, sensitivity varied unsystematically as a function of burst presence and/or transition deletion. Normal listeners appeared generally to make use of the transition cues more than did the hearing impaired. [Work supported in part by the U. S. Public Health Service.]

Initial stop voicing perception for cue‐adjusted syllables for impaired‐ and normal‐hearing listeners

Further work will be presented on voicing cues, specifically for initial stops, used by the hearing‐impaired. The set of test syllables /paed, kaed, taed, baed, gaed, daed/ was randomized 10 times on a list recorded by a male. Based on acoustical analyses, the potential sources of voicing cues in the syllables were: release‐burst duration, transition‐pattern of vowel onset, and vowel pitch. Among different conditions these cues in the syllables were modified cumulatively, so as to eliminate the contribution to voicing of each cue. The modifications were made through LPC resynthesis and/or waveform deletions. The conditions were administered monaurally at comfortable levels to six normal‐ and 21 impaired‐hearing adults. The syllables of each condition were presented in single‐interval identification trials without feedback. Generally, a similar pattern of results was seen between the impaired and the normal groups, although the impaired group performed somewhat poorer. Perception of initial stop voicing was unaf...

Vowel temporal masking of pitch recognition for consonant‐like noise bursts by normal‐ and impaired‐hearing listeners

Impaired‐ and normal‐hearing subjects (Ss) identified the pitch of either a low‐, mid‐, or high‐frequency noise burst in a recognition‐masking task with a two‐formant vowel masker which preceded and/or followed the noise burst. F1 of the vowel was at 700 Hz and F2 at 1100 Hz. The three noise bursts were bands of flat‐spectrum noise: 500–1500 Hz, 1500–4000 Hz, or 4000–6000 Hz. Forward‐, backward‐, and combined‐forward‐and‐backward‐masking conditions were tested with a 10 ms Δt. The vowel was presented at most comfortable listening level (MCL) for the impaired and at 90 dB SPL for the normal‐hearing Ss: the noise bursts were presented at 10 dB SL. Pitch recognition of the noise bursts was affected least in the backward‐masking condition and was poorest in the combined‐forward‐and‐backward‐masking condition. In the combined masking condition nearly all Ss showed some masking of pitch recognition for one or more of the noise bursts. Masking occurred most often for the low‐frequency burst and least often for t...