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Purpose: This study assessed the role of spectro-temporal modulation cues in the discrimination of 2 phonetic contrasts (voicing and place) for young infants., Method: A visual-habituation procedure was used to assess the ability of French-learning 6-month-old infants with normal hearing to discriminate voiced versus unvoiced (/aba/-/apa/) and labial versus dental (/aba/-/ada/) stop consonants. The stimuli were processed by tone-excited vocoders to degrade frequency-modulation cues while preserving: (a) amplitude-modulation (AM) cues within 32 analysis frequency bands, (b) slow AM cues only (<16 Hz) within 32 bands, and (c) AM cues within 8 bands., Results: Infants exhibited discrimination responses for both phonetic contrasts in each processing condition. However, when fast AM cues were degraded, infants required a longer exposure to vocoded stimuli to reach the habituation criterion., Conclusions: Altogether, these results indicate that the processing of modulation cues conveying phonetic information on voicing and place is "functional" at 6 months. The data also suggest that the perceptual weight of fast AM speech cues may change during development.

The role of spectro-temporal modulation cues in conveying tonal information for lexical tones was assessed in native-Mandarin and native-French adult listeners using a lexical-tone discrimination task. The fundamental frequency (F0) of Thai tones was either degraded using an 8-band vocoder that reduced fine spectral details and frequency-modulation cues, or extracted and used to modulate the F0 of click trains. Mandarin listeners scored lower than French listeners in the discrimination of vocoded lexical tones. For click trains, Mandarin listeners outperformed French listeners. These preliminary results suggest that the perceptual weight of the fine spectro-temporal modulation cues conveying F0 information is enhanced for adults speaking a tonal language.

The current study explored perception of prosody in normal and whispered speech using a two-interval, two-alternative forced-choice psychophysical task where listeners discriminated between French noun phrases pronounced as declaratives or interrogatives. Stimuli were either presented between 50 and 8000 Hz or filtered into one of three broad frequency regions, corresponding to harmonic-resolvability regions for normal speech (resolved, partially resolved, unresolved harmonics). Normal speech was presented against a speech-shaped noise masker, whereas whispered speech was presented in quiet. The results showed that discrimination performance was differentially affected by filtering for normal and whispered speech, suggesting that cues to prosody differ between speech modes. For whispered speech, evidence was mainly derived from the high-frequency region, whereas for normal speech, evidence was mainly derived from the low-frequency (resolved harmonics) region. Modeling of the early stages of auditory processing confirmed that for whispered speech, perception of prosody was not based on temporal auditory cues and suggests that listeners may rely on place of excitation (spectral) cues that are, in contrast with suggestions made by earlier work, distributed across the spectrum.

Purpose: The capacity of 6-month-old infants to discriminate a voicing contrast (/aba/-/apa/) on the basis of amplitude modulation (AM) cues and frequency modulation (FM) cues was evaluated., Method: Several vocoded speech conditions were designed to either degrade FM cues in 4 or 32 bands or degrade AM in 32 bands. Infants were familiarized to the vocoded stimuli for a period of either 1 or 2 min. Vocoded speech discrimination was assessed using the head-turn preference procedure., Results: Infants discriminated /aba/ from /apa/ in each condition; however, familiarization time was found to influence strongly infants' responses (i.e., their preference for novel vs. familiar stimuli)., Conclusions: Six-month-old infants do not require FM cues and can use the slowest (< 16 Hz) AM cues to discriminate voicing. Moreover, 6-month-old infants can use AM cues extracted from only 4 broad-frequency bands to discriminate voicing.

Speech perception of four phonetic categories (voicing, place, manner, and nasality) was investigated in children with specific language impairment (SLI) (n=20) and age-matched controls (n=19) in quiet and various noise conditions using an AXB two-alternative forced-choice paradigm. Children with SLI exhibited robust speech perception deficits in silence, stationary noise, and amplitude-modulated noise. Comparable deficits were obtained for fast, intermediate, and slow modulation rates, and this speaks against the various temporal processing accounts of SLI. Children with SLI exhibited normal "masking release" effects (i.e., better performance in fluctuating noise than in stationary noise), again suggesting relatively spared spectral and temporal auditory resolution. In terms of phonetic categories, voicing was more affected than place, manner, or nasality. The specific nature of this voicing deficit is hard to explain with general processing impairments in attention or memory. Finally, speech perception in noise correlated with an oral language component but not with either a memory or IQ component, and it accounted for unique variance beyond IQ and low-level auditory perception. In sum, poor speech perception seems to be one of the primary deficits in children with SLI that might explain poor phonological development, impaired word production, and poor word comprehension., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Young deaf children using a cochlear implant develop speech abilities on the basis of speech temporal-envelope signals distributed over a limited number of frequency bands. A Headturn Preference Procedure was used to measure looking times in 6-month-old, normal-hearing infants during presentation of repeating or alternating sequences composed of different tokens of /aba/and /apa/ processed to retain envelope information below 64 Hz while degrading temporal fine structure cues. Infants attended longer to the alternating sequences, indicating that they perceive the voicing contrast on the basis of envelope cues alone in the absence of fine spectral and temporal structure information.

Purpose: To investigate the capacity of young children and adults with normal hearing to discriminate speech on the basis of either relatively slow (temporal envelope, E) or fast (temporal fine structure, TFS) auditory cues., Method: Vowel-consonant-vowel nonsense disyllables were processed to preserve either the E or the TFS information in 16 adjacent frequency bands. The band signals were then recombined and resulting stimuli were presented for discrimination to adults or 5-, 6-, and 7-year-old children using an odd-ball paradigm. Discrimination scores (d') and response latencies were measured in each listener. No training was given to listeners., Results: Overall, discrimination scores were high (d' >or=1) in all speech-processing conditions, and did not differ across age groups. Overall, and irrespective of age, greater discrimination scores and shorter response latencies were observed for E speech than for TFS speech., Conclusions: These results suggest that normal-hearing children are able to encode and use E and TFS speech cues at adult levels by the age of 5 years. TFS- and E-coded speech stimuli might therefore prove to be a useful tool for the investigation of the developmental time course of speech perception, and for the early diagnosis of peripheral and central auditory processing disorders.

Recent work has demonstrated that auditory filters recover temporal-envelope cues from speech fine structure when the former were removed by filtering or distortion. This study extended this work by assessing the contribution of recovered envelope cues to consonant perception as a function of the analysis bandwidth, when vowel-consonant-vowel (VCV) stimuli were processed in order to keep their fine structure only. The envelopes of these stimuli were extracted at the output of a bank of auditory filters and applied to pure tones whose frequency corresponded to the original filters' center frequencies. The resulting stimuli were found to be intelligible when the envelope was extracted from a single, wide analysis band. However, intelligibility decreases from one to eight bands with no further decrease beyond this value, indicating that the recovered envelope cues did not play a major role in consonant perception when the analysis bandwidth was narrower than four times the bandwidth of a normal auditory filter (i.e., number of analysis bands > or =8 for frequencies spanning 80 to 8020 Hz).

Languages show systematic variation in their sound patterns and grammars. Accordingly, they have been classified into typological categories such as stress-timed vs syllable-timed, or Head- Complement (HC) vs Complement-Head (CH). To date, it has remained incompletely understood how these linguistic properties are reflected in the acoustic characteristics of speech in different languages. In the present study, the amplitude-modulation (AM) and frequency-modulation (FM) spectra of 1797 utterances in ten languages were analyzed. Overall, the spectra were found to be similar in shape across languages. However, significant effects of linguistic factors were observed on the AM spectra. These differences were magnified with a perceptually plausible representation based on the modulation index (a measure of the signal-to-noise ratio at the output of a logarithmic modulation filterbank): the maximum value distinguished between HC and CH languages, with the exception of Turkish, while the exact frequency of this maximum differed between stress-timed and syllable-timed languages. An additional study conducted on a semi-spontaneous speech corpus showed that these differences persist for a larger number of speakers but disappear for less constrained semi-spontaneous speech. These findings reveal that broad linguistic categories are reflected in the temporal modulation features of different languages, although this may depend on speaking style. [ABSTRACT FROM AUTHOR]

Purpose: Children with dyslexia have been suggested to experience deficits in both categorical perception (CP) and speech identification in noise (SIN) perception. However, results regarding both abilities are inconsistent, and the relationship between them is still unclear. Therefore, this study aimed to investigate the relationship between CP and the psychometric function of SIN perception. Method: Sixteen children with dyslexia, 16 chronological- age controls, and 16 reading-level controls were evaluated in CP of a voicing continuum and in consonant identification in both stationary and fluctuating noises. Results: There was a small but significant impairment in speech identification performance of children with dyslexia in stationary noise compared with chronological age--matched controls (but not reading level--matched controls). However, their performance increased in a fluctuating background, hence suggesting normal masking and unmasking effects and preserved sensory processing of speech information. Regarding CP, location of the phoneme boundary differed in the children with dyslexia compared with both control groups. However, scrutinizing individual profiles failed to reveal consistently poor performance in SIN and CP tasks. In addition, there was no significant correlation between CP, SIN perception, and reading scores in the group with dyslexia. Conclusions: The relationship between the SIN deficit and CP, and how they potentially affect reading in children with dyslexia, remains unclear. However, these results are inconsistent with the notion that children with dyslexia suffer from a low-level temporal processing deficit and rather suggest a role of nonsensory (e.g., attentional) factors in their speech perception difficulties. [ABSTRACT FROM AUTHOR]

The contribution of temporal fine structure (TFS) cues to consonant identification was assessed in normal-hearing listeners with two speech-processing schemes designed to remove temporal envelope (E) cues. Stimuli were processed vowel-consonant-vowel speech tokens. Derived from the analytic signal, carrier signals were extracted from the output of a bank of analysis filters. The “PM” and “FM” processing schemes estimated a phase- and frequency-modulation function, respectively, of each carrier signal and applied them to a sinusoidal carrier at the analysis-filter center frequency. In the FM scheme, processed signals were further restricted to the analysis-filter bandwidth. A third scheme retaining only E cues from each band was used for comparison. Stimuli processed with the PM and FM schemes were found to be highly intelligible (50–80% correct identification) over a variety of experimental conditions designed to affect the putative reconstruction of E cues subsequent to peripheral auditory filtering. Analysis of confusions between consonants showed that the contribution of TFS cues was greater for place than manner of articulation, whereas the converse was observed for E cues. Taken together, these results indicate that TFS cues convey important phonetic information that is not solely a consequence of E reconstruction. [ABSTRACT FROM AUTHOR]

Consonant identification was measured for a stationary and amplitude-modulated noise masker in four listeners with flat cochlear hearing loss, and four age-matched normal-hearing listeners. The masker modulation rate was systematically varied between 2 and 128 Hz. Masking release (MR), that is better identification performance in fluctuating, than in stationary noise, was highest in a masker fluctuating at 8–16 Hz in all normal-hearing listeners. In comparison, MR was only observed in two out of the four impaired listeners. In these listeners, MR was poorer than normal, and peaked at lower rates, that is 2 or 8 Hz. MR corresponded to increased reception of information for voicing, place, and manner between 2 and 64 Hz in all normal-hearing listeners. In impaired listeners, increased reception of information was mainly observed for manner, and mainly reduced for place, but these differences were not significant. For all phonetic features, MR was observed at lower masker fluctuation rates (≤32 Hz) than in normal-hearing listeners. This study therefore shows that cochlear damage affects MR, both quantitatively and qualitatively. [ABSTRACT FROM AUTHOR]