Purpose To evaluate potential contributions of broadband spectral integration in the perception of static vowels. Specifically, can the auditory system infer formant frequency information from changes in the intensity weighting across harmonics when the formant itself is missing? Does this type of integration produce the same results in the lower (F1) and higher (F2) regions? Does the spacing between the spectral components affect a listener’s ability to integrate the acoustic cues? Method Twenty young listeners with normal hearing identified synthesized vowel-like stimuli created for adjustments in the F1 (/ʌ/- /ɑ/, /ɪ/-/ɛ/) and in the F2 region (/ʌ/-/æ/). There were two types of stimuli: (1) two-formant tokens and (2) tokens in which one formant was removed and two pairs of sine waves were inserted below and above the missing formant; the intensities of these harmonics were modified to cause variations in their spectral center-of-gravity (COG). The COG effects were tested over a wide range of frequencies. Results Obtained patterns were consistent with calculated changes to the spectral COG, both in F1 and F2 regions. The spacing of the sine waves did not affect listeners’ responses. Conclusion The auditory system may perform broadband integration as a type of auditory wideband spectral analysis.

This study considers an operation of an auditory spectral integration process which may be involved in perceiving dynamic time-varying changes in speech found in diphthongs and glide-type transitions. Does the auditory system need explicit vowel formants to track the dynamic changes over time? Listeners classified diphthongs on the basis of a moving center of gravity ͑COG͒ brought about by changing intensity ratio of static spectral components instead of changing an F2. Listeners were unable to detect COG movement only when the F2 change was small ͑160 Hz͒ or when the separation between the static components was large ͑4.95 bark͒.

This study examines speech perception in multi-talker babble by varying speaker dialect as a masker. Studies varying the language of the target speech and the babble masker show that the target is most intelligible when the masker is constructed from a non-native language and target represents exemplars from the listener’s native language. Does variation in speaker and listener dialect has a similar effect on speech intelligibility? In this study, central Ohio listeners listen to target sentences spoken by either native Ohio or native North Carolina talker. The sentences are masked by multi-talker babble consisting of speech from either Ohio or North Carolina talkers presented at several sound-to-babble (S/B) ratios. The same material is also presented to listeners in North Carolina. The results for Ohio listeners show significant effects of dialect at 0 dB S/B ratio. Intelligibility improved when the background babble featured the dialect that was different from the dialect of the target speaker. The performance of Ohio listeners was more than 20% higher when the target was presented in the North Carolina babble than in the Ohio babble. Results for North Carolina listeners will be discussed. [Work supported by NIH.]

The center-of-gravity (COG) hypothesis proposed by Chistovich and others for the perception of static vowels suggests that auditory spectral integration may occur when two or more formants fall within a 3.5 bark bandwidth. While several studies have examined the bandwidth limits of such integration, this study examines the extent to which spectral integration is uniform within this putative 3.5-bark range. We examine the perceptual salience of virtual formants produced by modifying the spectral COG of two closely spaced narrow-bandwidth resonances. Three different vowel series were created: [i-■], [■-■] and [■-■]. A second set of vowels was then created in which one of the formants (F1 in [i-■], F2 in [■-■] and F3 in [■-■]) was replaced by a virtual formant whose COG matched that of the formant that had been removed. The frequency separation between the two component resonances was then systematically varied between 1.5 and 3.5 barks and a singleinterval 2AFC vowel identification task was used to obtain estimates of vowel quality for each series step. Results will be discussed in terms of whether the spectral integration effects within the 3.5 bark decline as the frequency separation between the resonance components increases. [Work supported by NIDCD R01DC00679-01A1.]

The acoustic properties of four lexical tones between two regional varieties of Mandarin Chinese, Beijing Mandarin (Putonghua), and Taiwan Mandarin (Guoyu) were examined in terms of duration, pitch contours, and rms amplitude. Tokens included CV and V monosyllables, representing each of the four tones of Mandarin Chinese, and were produced in isolation and in sentence context by 15 adult native speakers. A different durational pattern of citation tones emerged for two dialect variety groups. In Taiwan Mandarin, it was T2>T1>T3>T4; whereas, it was T3>T2>T1>T4 in Beijing Mandarin [Deng et al. (2006)]. The durational discrepancy in isolated T3 may be related to different realization of T3 between two dialect groups. While T3 exhibited a falling-rising pitch contour in Beijing Mandarin, it was falling in Taiwan Mandarin. Such dialectal divergence in T3 contours shapes can be verified from the amplitude contours. Furthermore, pitch contours of other tones in two dialects will be compared to see if there is tonetic sound change in other Taiwan Mandarin tones. These surface acoustic variations in linguistically identical categories can result in perceptually ambiguous tones. A gating experiment was utilized to examine how native and non-native listeners adapt to speaker and dialect variability in the stimuli.