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5SP4. Chan ges in open and spced ąuotient values as a function of measurement criteria. Christine M. Sapienza, Elaine T. Stathopoulos (Stare Univ. of New York at Buffalo, Amherst, NY 14260), and Christopher Dromey (Royal Victoria Hospital)

Noninvasive measures of vocal-fold aclivity have become useful in describing normal and disordered voice production. Specifically, open and speed quotient measures (OQ and SQ) of electroglottographic and inverse filtered airflow waveforms have been used to describe variability in the phases of vocal-fold vibration. Unfoiiunatcly, there is little con-sislency in the criteria used to calculate these quotients. The lack of consistency becomes important when comparing quotient values from similar waveforms (e.g., VFCA waveform) as well as different types of wavcforms (e.g., VFCA versus glottal airflow). Four different percent-age criteria were chosen to investigate how quotient values change within and across signal types. Twenty pcrcent, 50%, 80%, and 100% of the ac pcak-to-peak amplitudę of electroglottographic and glottal airflow waveforms were selccted. Kesults indicated different values ob-tained across criteria levels. Comparison of absolute values from quo-tient data across criteria or signal type is not recommended. Use of common measurement procedures is needed so that normative data can be established. (Work supported by NIH #DC005l6-42.( 5SP5. Minimal spectral contrast for vowel recognition as a function of spectral słope. Andrew Lea and Quentin Summerfield (MRC Inst. of Hearing Res., University Park, Nottingham NG7 2RD, U.K.)

Can listeners locate formants not only from peaks in the cnvclope of the excitation pattem of a vowel, but also from “shoulders"—fcatures giving risc to zero crossings in the third, but not the first, differential of the excitation pattern—as hypothesized by Assmann and Summerfield (J. Acoust. Soc. Am. 85, 327-338 (1989)]? Stimuli were steady-state approximations to the vowels /a, i, 3, u/ created by summing the first 45 harmonics of 100 Hz. Thirty-ninc harmonics had cqual amplitudes; the other six formed three pairs that were raised to definc three “formants." An adaptive psychophysical procedurę determined the minimal differ-ence in level between the 6 harmonics and the remaining 39 at which the vowels were identifiably different from one another. These thresholds were measured through simulated communication channels giving over-all slopes to the excitation pattems of the vowcls ranging from — I dB/erb to + 2 dB/erb. Excitation pattems of the threshold stimuli were computed and the locations of formants were estimated from zero crossings in the first and third differentials. With sloping frequency responses, some formants of some vowels were represented as shoulders rather than peaks, confirming Assmann and Summerfield’s hypothesis. Implications for models of fonnant extraction will be discussed.

5SP6. ARe differcnces in the processinR of dynamie acoustic Information. Robert A. Fox, Lida G. Wall, and Jeanne Gokcen (Div. of Speech and Hearing Sci., Ohio State Univ., 110 Pressey Hall, Columbus, OH 43210-1002)

The present study examines possible age-related differcnces in the use of dynamie acoustic information (in the form of formant transi-tions) to identify CVC words. Sixty-two high-frequency monosyllabic English words were recorded that began or ended in orał or nasal stops. From these words, two sets of tokens were created: an unmodified CVC token representing the whole word and a silent-center version in which approximately 70% of the medial vowel was replaced by silence. Two sets of listeners were required to identify these words in first the silent-center condition and then the whole-word condition. The listeners in-cluded 17 college sophomores or juniors and 22 older subjects aged 55-75. Ali listeners wcrc screcncd for normal auditory scnsitivity. Re-sults demonstrated bolh age groups* identifications were somewhat bet-ter in the whole-word condition than in the silent-center condition. However, the mean correct consonant and vowel identifications of the older listener group was approximately 10% less than that for the younger listeners in the silent-center condition. No age difference was obtained in the whole-word condition. These data support the hypothesis that older listeners have greater difficulty than younger listeners in Processing dynamie acoustic information in the pcrception of speech. (Supported by NI A Grant #1 ROI AG08353-01.] 5SP7. Evidence for a rhyme and onset model of lexical access in children. W. D. Murphy (Psychology Dept., Univ. of Rochester, Rochester. NY 14627), L. Gerkcn (SUNY at Buffalo, NY), R. P. Cooper (Virginia Tech., VA), and R. N. Aslin (Univ. of Rochester, NY)

A previous report (Murphy et ai, J. Acoust. Soc. Am. Suppl 1 87, S73 (1990)] indicated that 4-year olds do not process spoken words and non words in a strict left-to-right manner. Instead, in a matching task they appear to search for the longest uninlerrupted scquencc of seg-ments or to use a rhyming strategy. This poster reports the results of two subsequent studies designed to determine which of these two strat-egies was employed. The first follow-up study presented children with comparison items that shared the same number of uninterrupted seg-rnents as the target word (“little"). Some comparison items rhymed with the target (“gittle"), and others did not (“litten”). Results did not support the uninterrupted-segment matching model but were consistent with the rhyming model. A second follow-up study used monosyllabic stimuli. Results suggested that (I) children treat words with semivowel second syllable consonants as monosyllabic. and (2) both rhyme and similarity of the onset consonant-vowel sequence play a role in Iexical access.

5SP8. Effect of consonant-vowel intensity ratio on the intelligibility of spectrally degraded speech. Urna Balakrishnan, Richard L. Freyman, Chiang Yuan Chuan, G. Patrick Nerbonnc, and Kelly J. Shca (Dept. of Commun. Disord., Univ. of Massachusetts, Amherst, MA 01003)

Normal-heanng subjects’ recognition of spectrally degraded speech was evaluated under conditions where the waveform envelope was mod-ified by altering the consonant-vowel intensity (C-V) ratios. Subjects were rcquired to identify 22 consonants presented in the /a-Consonant-a/ format at suprathreshold and near threshold levels of presentation. In both conditions, the stimuli were processed to limit spectral information. In the suprathreshold condition, stimuli were presented at the natural C-V ratio and at six modified C-V ratios. In the near threshold conditions, three C-V ratios were employed—the natural ratio and two altered C-V ratios. The effect of C-V ratio modifica-tion on recognition performance varicd across consonants. Within groups of consonants, “high” or “Iow” C-V ratios predisposed listeners to select certain consonants as the response. For cxample, for high C-V ratios of the stimuli /afa/ and /asa/, listeners selected /asa/ as the response. For Iow C-V ratios of these consonants, the predoininant response was /afa/. Similar C-V ratio-dependent responses were also obtained for the glidc and nasal consonant groups. Finally, for some consonants such as the stops, C-V ratio modification did not affect recognition performance. Results from both studies suggesł that in the absence of spectral information, listeners depend on the envelope cues available in the speech waveform for speech sound recognition. (Work supported by the Whilaker Foundation.] 5SP9. The influence of segmental sonority on immediate memory for syllables. Shari R. Speer (Dept. of Psychol., Northeastcrn Univ., 360 Huntington Ave., Boston, MA 02115) and Aimee M. Surprenant (Yale University, New Haven, CT)

Four experiments demonstrate that the sonority of a syllable’s com-ponent sounds prediets the presence and magnitude of recency effects in immediate memory. Sonority is determined by co-occurrence restric-tions on vowel and consonant sounds within syllable-internal structure. Recency effects were most pronounced in memory for CV strings with

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J. Acoust. Soc. Am., Voł. 89, No. 4, Pt. 2, April 1991

121st Meeting: Acoustical Society of America

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