Lisa Holden‐Pitt

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.

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.

Toward understanding the role of formant transitions for distinctions of stops from glides

Our understanding is incomplete of the properties of vowel formant transitions that contribute to distinctions of voiced stop and glide consonants in speech. Research appears to have established some of the important transition cues for discernment of bilabial synthetic stops versus glides. However, the stop/glide transitions studied have typically been more stylized than those found in natural speech. This investigation examined the importance of transitions to listeners’ identification of initial stops and glides in spoken /CVk/ syllables. Performance was assessed for the stops and glides with progressive deletion of segments from the syllables’ onsets. Bilabial and velar stops and glides as well as alveolar stops were tested in /Ci/, /Copen ayek/, /Cash, ligaturek/ contexts to examine differences in transition use among phoneme environments. Twelve normal‐hearing young adults participated as listeners. In general, when the initial stop bursts were deleted, the F2 transition frequency extent was signifi...

Predicting hearing‐impaired listeners’ use of acoustic cues for consonant recognition

Reduced consonant recognition and large inter‐listener variability among individuals with sensorineural hearing loss are neither well characterized nor understood. Previous attempts to account for consonant recognition using threshold and suprathreshold measures have produced equivocal results. Classifications of listeners according to performance patterns for acoustic cue use are lacking. The present study classifies hearing‐impaired listeners according to their use of information in successive vowel and consonant segments for identification of consonants. Seventy hearing‐impaired (moderate to profound) and 19 normal‐hearing listeners identified /n/, /l/, and /d/ in spoken VCV’s extracted from connected speech. The VCV’s were presented unmodified and with consonant and vowel‐transition segment deletions. Percent information transmitted scores for each consonant and stimulus condition were submitted to a hierarchical cluster analysis to classify all listeners into homogeneous groups based on the extent to...

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.

Temporal and spectral cue use for initial‐stop voicing perception by hearing‐impaired and normal‐hearing children and adults

VOT cue use was assessed using a DAD‐TAD stimulus continuum developed from computer‐edited spoken [taed] and [daed]. Within continua, stimuli contained progressively longer durations of the [t] burst extracted from [taed]; use of vowel onset cues was assessed via continua differing for the vowel stem (from [taed] or [daed]) to which these bursts of progressively increased duration were appended. Identification of these stimuli was assessed in hearing‐impaired children (n = 16) and adults (n = 20), and normally hearing children (n = 10) and adults (n = 5). Of the hearing‐impaired, only 6 children and 15 adults correctly identified the endpoints of the VOT continua; for these listeners, voicing boundaries assumed longer VOT values than for normal‐hearing listeners. The width of the phonemic boundary region widened from the normal‐hearing adults to the hearing‐impaired children. Cues in the vowel did appear to affect VOT boundaries for all listener groups, but less for the normal‐hearing children and hearing‐impaired adults than for the normal‐hearing adults, and least for the hearing‐impaired children.

Cue salience in the perception of a stop voicing contrast by hearing and hearing‐impaired children

The contribution of two acoustic cues, voice onset time (VOT) and vowel onset frequencies, to the perception of a TAD‐DAD voicing contrast was examined for ten normal‐heating and six hearing‐impaired children (3 FA: 50–95 dB HL) between 6 and 12 years of age. Both natural stimuli and high‐quality synthesized copies of these stimuli were used to create five VOT continua (three natural and two synthetic), in which the vowel onset cue was either appropriate or conflicting. An adaptive identification procedure was used to determine phoneme boundaries under these five test conditions. Changes in spectral characteristics at vowel onset did produce significant shifts in phoneme boundary for the normal‐hearing group, but not for the hearing‐impaired group. Similar phoneme boundaries were obtained by the normal‐hearing group for natural continua and their synthetic counterparts. However, higher values of standard error were observed for synthetic stimuli for both listener groups.

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...