Wurm and A. G. Samuel, J. Acoust. Soc. ... Bashford, Jr., Richard M. Warren, and Chris A. Brown (Psychol. Dept. ... recent studies [e.g., A. G. Samuel, J. Mem.
Previous work [Frauenfelder et al, JEP:HPP 16, 77-91 (1990)] tested a critical prediction of the TRACE model of speech perception [J. L. McClelland and J. L. Elman, Cog. Psychol. 18, 1-86 (1986)]. Frauenfelder et al found no evidence of inhibitory lexical effects on performance of a phoneme monitoring task, and concluded that the TRACE model was inaccurate. However, recent experiments [L. H. Wurm and A. G. Samuel, J. Acoust. Soc. Am. 94, 1883(A) (1993)] showed that the earlier conceptualization of the problem had several limitations, and that the question of inhibitory lexical effects was still unanswered. This experiment extends that work, examining specifically the role of attentional allocation during the phoneme monitoring task. In dual-task paradigm [e.g., M. I. Posner and S. J. Boies, Psychol. Rev. 78, 391-408 (1971)], stimuli were presented dichotically to subjects, who simultaneously monitored for specified phoneme targets in speech and for frequency modulations in a pure tone. Reaction times to frequency modulations were measured as a function of their locations relative to phoneme changes in nonword stimuli. The results of this line of research clarify the role played by attentional processes during speech perception, and whether indirect lexical inhibition should be included in models of lexical access. [Work supported by AFOSR.] 4pSP10. The effect of discriminability on dimensional interactions of pitch with vowel and consonant identity. Aimee M. Surprenant and Diane Kewley-Port (Dept. of Speech and Hear. Sci., Indiana Univ., Bloomington, IN 47405) The ability to ignore irrelevant variation in the speech signal is essential for normalizing across speakers and situations. Past research has indicated that irrelevant variation in such features as pitch and vowel quality caused more interference on a consonant classification task than the reverse. Along with other more memory-oriented paradigms such as serial-list recall, this has been taken as evidence that the longer-lasting, periodic elements of sound that make up vowel and pitch information remain longer in auditory memory, thereby interfering with judgments about consonant identity. However, in most of these demonstrations, the relative discriminability of the tokens was not controlled. In the present study, discriminability was assessed for continua of pitch, consonant and vowel identity for stop-vowel syllables. Eight welltrained subjects were asked to make speeded same-different judgments on one dimension of stimuli that varied on two dimensions. An interaction for both response time and accuracy was found such that as the discriminability of the relevant dimension was increased, interference from the irrelevant dimension decreased and vice versa. Although there were minor variations, the same general pattern was observed in all conditions. [Research supported by NIDCD.] 4pSPll. Researchers beware: Use of speech-modulated noise adds strong "bottom-up" cues to phonemic restoration. James A. Bashford, Jr., Richard M. Warren, and Chris A. Brown (Psychol. Dept., Univ. of Wisconsin—Milwaukee, Milwaukee, WI 53201) When deleted segments of speech are replaced by extraneous sound, the missing speech fragments may be perceptually restored and intelligibility improved. This phonemic restoration (PhR) effect has been used to measure various aspects of speech processing, with deleted portions of speech typically replaced by Gaussian noise. However, several recent studies [e.g., A. G. Samuel, J. Mem. Lang. 26, 36-56 (1987)] used noise that followed the amplitude envelope of the speech fragment, providing precise moment-by-moment control over the signal/noise ratio, but also possibly providing envelope cues concerning the replaced speech. The present study examined this possibility by comparing the effects of Gaussian noise and speech-modulated noise interrupters upon the restoration of intelligibility. Filling periodic interruptions in sentences with modulated noise produced twice the intelligibility increase obtained with Gaussian noise. Further, when isolated monosyllables were interrupted, interpolation of modulated noise increased intelligibility whereas Gaussian noise reduced intelligibility. It is suggested that, although the enhancement of intelligibility of speech-modulated noise is an interesting topic, the results obtained with the stimulus are confounded by the addition of bottom-up information not present when PhRs are produced by independent extraneous sounds. [Work supported by NIH.] 2975
J. Acoust. Soc. Am., Vol. 95, No. 5, Pt. 2, May 1994
4pSP12. Spectral restoration of speech by noise. Keri R. Riener, Richard M. Warren, and James A. Bashford, Jr. (Psychol. Dept., Univ. of Wisconsin—Milwaukee, Milwaukee, WI 53201) Two types of perceptual synthesis (or auditory induction) have been reported that can minimize or cancel the effects of masking upon speech: Phonemic restoration can enhance intelligibility of speech when segments are replaced or masked by noise, and contralateral induction can prevent mislateralization of speech masked at one ear [see R. M. Warren, Psychol. Bull. 96, 371-383 (1984)]. A third type of auditory induction, "spectral restoration," is reported, which can enhance intelligibility when deleted regions of the speech spectrum are replaced by noise. Separate groups of listeners heard lists of sentences consisting of two widely separated bands having low intelligibility. When an appropriate noise was added to the spectral gap separating the bands, a significant improvement in intelligibility was observed. It is suggested that spectral restoration represents a mechanism capable of enhancing comprehension of speech when portions of its spectrum are masked. 4pSP13. Perceptual normalization of speech and nonspeech. Mark A. Pitt (Dept. of Psychol., Ohio State Univ., 1885 Neil Ave., Columbus, OH 43210) Within the information processing approach to speech perception, the problem of acoustic-phonetic variability is solved by positing multiple stages of processing that transform the acoustic input into a stable phonetic percept. If this problem is viewed as part of the broader problem of perceptual normalization, a question that arises is whether the mechanisms that normalize speech stimuli also normalize nonspeech stimuli. Five experiments addressed this question by investigating the normalization of musical timbre using a selective adaptation paradigm. The results parallel some of those found with speech, suggesting that a single mechanism normalizes both types of stimuli. 4pSP14. The representation of the place of nasal stops in word recognition. James T. Myers and Paul A. Luce (Dept. of Psychol., SUNY at Buffalo, Buffalo, NY 14260) Predictable aspects of the representations used in the perception of a word may not be necessary for recognition of the word to be successful. The present study investigates whether relative predictability of place in nasal stops affects recognition of words. Subjects were given an auditory lexical decision task in which each target time was preceded by an auditory prime. Target words ended in / m p / (BUMP), / n t / (BUNT), / m / (BUM), or / n / (BUN). Primes ended in / m / (UM), / n l / (UN), or / k / (UK). Place of the nasal stops is predictable in / m p / and / n t / words given the place of the following obstruent. Some current theories of phonological underspecification also claim that place in / n / words is predictable, assuming that coronal is universally the default place. It was found that /mp/, /nt/, and / n / words were primed equally well by / m / and / n / primes, implying that the specifics of place were not relevant in these words. By contrast, / m / words were primed significantly better by / m / primes relative to / n / primes, implying that the representation of place in / m / words is relevant for recognition. [Work supported by NIDCD.] 4pSP15. Bimodal perception of spectrum compressed speech. Larry D. Paarmann (Dept. of Elec. Eng., Wichita State Univ., Wichita, KS 67260-0044), Michael K. Wynne (Indiana Univ. School of Medicine, Indianapolis, IN), Carmen M. Pugh (Wichita Clinic, Wichita, KS), and Jun Bi (WeatherData, Inc., Wichita, KS) In this study, ten normal-hearing adult listeners were asked to identify CUNY nonsense syllables presented auditorily and bimodally (audition and vision) via video tape in two conditions: Low-pass filtered and spectrum compressed by means of nonlinear sampling in the frequency domain [L. D. Paarmann, M. D. Guiher, and M. K. Wynne, J. Comp. Users Speech and Hear. 7, 257-281 (1991)]. The data collected were analyzed using a 2X2 ANOVA to determine if significant differences exist across the two main effects and if the interaction between the variables is significant. Although this study does not directly address the effectiveness of spectrum compression of the speech signal to improve speech understanding for hearing-impaired listeners, the results do strongly support the hypothesis that spectrum compressed speech is 127th Meeting: Acoustical Society of America
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