SHORT-TERM PERCEPTUAL TUNING TO TALKER CHARACTERISTICS.

When a listener encounters an unfamiliar talker, the ensuing perceptual accommodation to the unique characteristics of the talker has two aspects: (1) the listener assesses acoustic characteristics of speech to resolve the properties of the talker's sound production; and, (2) the listener appraises the talker's idiolect, subphonemic phonetic properties that compose the finest grain of linguistic production. A new study controlled a listener's exposure to determine whether the perceptual benefit rests on specific segmental experience. Effects of sentence exposure were measured using a spoken word identification task of Easy words (likely words drawn from sparse neighborhoods of less likely words) and Hard words (less likely words drawn from dense neighborhoods of more likely words). Recognition of words was facilitated by exposure to voiced obstruent consonants. Overall, these findings indicate that talker-specific perceptual tuning might depend more on exposure to phonemically marked consonants than to exposure distributed across the phoneme inventory.

Constraints on Sensitivity to Auditory Modulation in the Perceptual Organization of Speech.

BACKGROUND/STUDY CONTEXT: The perception of speech requires the integration of sensory details from a rapidly fading trace of a time-varying spectrum. This effortful cognitive function has been difficult to assess. New tests measuring intelligibility of sine-wave replicas of speech provided an assay of this critical function in normal-hearing young adults. METHODS: Four time-varying sinusoids replicated the frequency and amplitude variation of the natural resonances of spoken sentences. The temporal tolerance of perceptual integration of speech was measured by determining the effect on intelligibility of desynchronizing a single sine-wave component in each sentence. This method was applied in tests in which the sentences were temporally compressed or expanded over a 40% range. RESULTS: Desynchrony was harmful to perceptual integration over a narrow temporal range, indicating that modulation sensitivity is keyed to a rate of 20 Hz. No effect of variation in speech rate was observed on the intelligibility measure, whether rate was accelerated or decelerated relative to the natural rate. CONCLUSION: Performance measures of desynchrony tolerance did not vary when speech rate was accelerated or decelerated, revealing constraints on integration that are arguably primitive, sensory, auditory, and fixed. Because these are not adaptable, they limit the potential for perceptual learning in this aspect of perceptual organization. Implications for describing the elderly listener are noted.

Modulation sensitivity in the perceptual organization of speech.

In a spoken utterance, a talker expresses linguistic constituents in serial order. A listener resolves these linguistic properties in the rapidly fading auditory sample. Classic measures agree that auditory integration occurs at a fine temporal grain. In contrast, recent studies have proposed that sensory integration of speech occurs at a coarser grain, approximate to the syllable, on the basis of indirect and relatively insensitive perceptual measures. Evidence from cognitive neuroscience and behavioral primatology has also been adduced to support the claim of sensory integration at the pace of syllables. In the present investigation, we used direct performance measures of integration, applying an acoustic technique to isolate the contribution of short-term acoustic properties to the assay of modulation sensitivity. In corroborating the classic finding of a fine temporal grain of integration, these functional measures can inform theory and speculation in accounts of speech perception.

Early recognition of speech.

Classic research on the perception of speech sought to identify minimal acoustic correlates of each consonant and vowel. In explaining perception, this view designated momentary components of an acoustic spectrum as cues to the recognition of elementary phonemes. This conceptualization of speech perception is untenable given the findings of phonetic sensitivity to modulation independent of the acoustic and auditory form of the carrier. The empirical key is provided by studies of the perceptual organization of speech, a low-level integrative function that finds and follows the sensory effects of speech amid concurrent events. These projects have shown that the perceptual organization of speech is keyed to modulation; fast; unlearned; nonsymbolic; indifferent to short-term auditory properties; and organization requires attention. The ineluctably multisensory nature of speech perception also imposes conditions that distinguish language among cognitive systems. WIREs Cogn Sci 2013, 4:213-223. doi: 10.1002/wcs.1213 This article is categorized under: Psychology > Language.

Estimating speech spectra for copy synthesis by linear prediction and by hand.

Linear prediction is a widely available technique for analyzing acoustic properties of speech, although this method is known to be error-prone. New tests assessed the adequacy of linear prediction estimates by using this method to derive synthesis parameters and testing the intelligibility of the synthetic speech that results. Matched sets of sine-wave sentences were created, one set using uncorrected linear prediction estimates of natural sentences, the other using estimates made by hand. Phoneme restrictions imposed on linguistic properties allowed comparisons between continuous and intermittent voicing, oral or nasal and fricative manner, and unrestricted phonemic variation. Intelligibility tests revealed uniformly good performance with sentences created by hand-estimation and a minimal decrease in intelligibility with estimation by linear prediction due to manner variation with continuous voicing. Poorer performance was observed when linear prediction estimates were used to produce synthetic versions of phonemically unrestricted sentences, but no similar decline was observed with synthetic sentences produced by hand estimation. The results show a substantial intelligibility cost of reliance on uncorrected linear prediction estimates when phonemic variation approaches natural incidence.