Noise thresholds in harmonic series maskers.

The presence of noise is a salient cue to the perception of breathiness and aspiration in speech sounds. The detection of noise within harmonic series (maskers) composed of unresolved components was found to depend on the fundamental frequency (fo) and the overall level of the masker [Gockel, Moore, and Patterson (2002). J. Acoust. Soc. Am., 111 (6), 2759-2770]. In the present study, noise detection thresholds were measured as a function of the frequency range, the fo, and the overall level of harmonic maskers. Frequency range was specified in equivalent rectangular bandwidth (ERB) units (3-13, 13-23, 23-33, or 3-33 ERBs). The results were consistent with the idea that listeners rely on spectral cues when maskers comprise only resolved components (3-13 ERBs), and on temporal (dip listening) cues when maskers contain only unresolved components (23-33 ERBs). Noise detection thresholds were generally lower when masker level was high (70 dBA) than when it was low (50 dBA). Masker fo affected thresholds only when listeners relied on spectral cues for noise detection. With the wideband (3-33 ERBs) masker, listeners likely detected noise by focusing on the frequency band (23-33 ERBs) with the most advantageous noise-to-harmonic ratio.

The effect of vocal tract parameters on aspiration noise discrimination.

Previous research showed that aspiration noise difference limens in moderately breathy /a/ vowels decreased as the spectral slope of the glottal source spectrum became increasingly steep [Kreiman and Gerratt, J. Acoust. Soc. Am. 131(1), 492-500 (2012)]. The current study investigated whether discrimination of aspiration noise levels was affected by differences in spectral shape due to vowel quality (/æ/ and /i/) and speaker identity (three male speakers) when the slope of the glottal source spectrum was fixed. The results showed that discrimination performance was worse overall for /i/ than /æ/, but the result may have resulted from relatively poor performance for the /i/ vowel of one speaker. Acoustic analyses of the stimuli were performed to estimate the association between acoustic properties and the perceptual outcomes. The results showed that both the smoothed cepstral peak prominence and the harmonic energy level between 2 and 5 kHz may account for the observed differences in aspiration noise discrimination among speakers within each vowel, but not for differences between vowel categories. It is possible that the relationship between the aspiration noise discrimination and aforementioned acoustic properties may be modulated by the spectral distribution of energy across frequency.

Pitch perception and production in congenital amusia: Evidence from Cantonese speakers.

This study investigated pitch perception and production in speech and music in individuals with congenital amusia (a disorder of musical pitch processing) who are native speakers of Cantonese, a tone language with a highly complex tonal system. Sixteen Cantonese-speaking congenital amusics and 16 controls performed a set of lexical tone perception, production, singing, and psychophysical pitch threshold tasks. Their tone production accuracy and singing proficiency were subsequently judged by independent listeners, and subjected to acoustic analyses. Relative to controls, amusics showed impaired discrimination of lexical tones in both speech and non-speech conditions. They also received lower ratings for singing proficiency, producing larger pitch interval deviations and making more pitch interval errors compared to controls. Demonstrating higher pitch direction identification thresholds than controls for both speech syllables and piano tones, amusics nevertheless produced native lexical tones with comparable pitch trajectories and intelligibility as controls. Significant correlations were found between pitch threshold and lexical tone perception, music perception and production, but not between lexical tone perception and production for amusics. These findings provide further evidence that congenital amusia is a domain-general language-independent pitch-processing deficit that is associated with severely impaired music perception and production, mildly impaired speech perception, and largely intact speech production.

Performance of speech-language pathology students in problem-based learning tutorials and in clinical practice.

The purpose of the study was to identify if performance of speech-language pathology students in problem-based learning (PBL) tutorials could predict subsequent clinical performance evaluated through (a) a non-standardized, custom clinical evaluation form (HKU form) and (b) a standardized competency assessment for speech pathology developed in Australia (COMPASS®). Students' scores from PBL tutorial performance were correlated with scores in clinical placement on both the HKU form and the COMPASS. Significant correlations were found between students' PBL tutorial performance (reflective journals and participation in the tutorial process) and their clinical performance (treatment and interpersonal skills) on the HKU clinical evaluation form. Significant correlations were also found between (a) PBL tutorial performance (participation in the tutorial process) and their clinical performance (all generic and occupational competencies, and the overall score) on the COMPASS, (b) PBL tutorial performance (reading forms) and two occupational competencies on the COMPASS, (c) PBL tutorial performance (reflective journals) and four occupational competencies and the overall score on the COMPASS. The results highlighted the need for validating the assessment for the learning process in PBL tutorials with empirical evidence and the advantage of assessing clinical performance through COMPASS in Hong Kong. Tutors, clinical supervisors and students should be given clear behavioral descriptors for expected performance in PBL tutorials and clinical practice at different year levels.

Are tones phones?

The psycholinguistic status of lexical tones and phones is indexed via phonological and tonological awareness (PA and TA, respectively) using Thai speech. In Experiment 1 (Thai participants, alphabetic script and orthographically explicit phones/tones), PA was better than TA in children and primary school-educated adults, and TA improved to PA levels only in tertiary-educated adults. In Experiment 2 (Cantonese participants, logographic script and no orthographically explicit phones/tones), children and primary-educated adults had better PA than TA, and PA and TA were equivalent in tertiary-educated adults, but were nevertheless still below the level of their Thai counterparts. Experiment 3 (English-language participants, alphabetic script and nontonal) showed better PA than TA. Regression analyses showed that both TA and PA are predicted by reading ability for Thai children but by general nonorthographic age-related variables for Cantonese children, whereas for English children reading ability predicts PA but not TA. The results show a phone>tone perceptual advantage over both age and languages that is affected by availability of orthographically relevant information and metalinguistic maturity. More generally, both the perception and the psycholinguistic representation of phones and tones differ.

The effects of tongue loading and auditory feedback on vowel production.

This study investigated the role of sensory feedback during the production of front vowels. A temporary aftereffect induced by tongue loading was employed to modify the somatosensory-based perception of tongue height. Following the removal of tongue loading, tongue height during vowel production was estimated by measuring the frequency of the first formant (F1) from the acoustic signal. In experiment 1, the production of front vowels following tongue loading was investigated either in the presence or absence of auditory feedback. With auditory feedback available, the tongue height of front vowels was not modified by the aftereffect of tongue loading. By contrast, speakers did not compensate for the aftereffect of tongue loading when they produced vowels in the absence of auditory feedback. In experiment 2, the characteristics of the masking noise were manipulated such that it masked energy either in the F1 region or in the region of the second and higher formants. The results showed that the adjustment of tongue height during the production of front vowels depended on information about F1 in the auditory feedback. These findings support the idea that speech goals include both auditory and somatosensory targets and that speakers are able to make use of information from both sensory modalities to maximize the accuracy of speech production.

The perception of intonation questions and statements in Cantonese.

In tone languages there are potential conflicts in the perception of lexical tone and intonation, as both depend mainly on the differences in fundamental frequency (F0) patterns. The present study investigated the acoustic cues associated with the perception of sentences as questions or statements in Cantonese, as a function of the lexical tone in sentence final position. Cantonese listeners performed intonation identification tasks involving complete sentences, isolated final syllables, and sentences without the final syllable (carriers). Sensitivity (d' scores) were similar for complete sentences and final syllables but were significantly lower for carriers. Sensitivity was also affected by tone identity. These findings show that the perception of questions and statements relies primarily on the F0 characteristics of the final syllables (local F0 cues). A measure of response bias (c) provided evidence for a general bias toward the perception of statements. Logistic regression analyses showed that utterances were accurately classified as questions or statements by using average F0 and F0 interval. Average F0 of carriers (global F0 cue) was also found to be a reliable secondary cue. These findings suggest that the use of F0 cues for the perception of intonation question in tonal languages is likely to be language-specific.

Perceived tonal continuity through two noise bursts separated by silence.

Three experiments measured the perceived continuity of two pure tones "flankers" through a masker containing a silence. Experiment 1 used a 2I-2AFC procedure; one interval contained two noise bursts separated by a silent gap, and the other contained two noise bursts separated by a tone of the same duration as the silence. Discrimination between masker conditions was very accurate when the flankers were absent but was impaired substantially when the flankers were present. This was taken as evidence that illusory flanker continuity during the silent gap was heard as similar to the physical presence of a tone in the gap. In experiment 2, performance remained poor when the flankers were frequency glides aligned along a common trajectory. Performance improved significantly when the flankers were misaligned in trajectory. In experiment 3, listeners rated directly perceived flanker continuity. Strong continuity was reported in the silent gap conditions for which poor performance had been observed in experiments 1 and 2. These findings show that continuity may be heard through a masker that cannot mask a physically continuous tone but can mask the flankers' offset and onset. The results are explained in terms of the perceptual grouping of onsets and offsets of the flankers.

Phonemic restoration of interrupted locally time-reversed speech : Effects of segment duration and noise levels.

Intelligibility of temporally degraded speech was investigated with locally time-reversed speech (LTR) and its interrupted version (ILTR). Control stimuli comprising interrupted speech (I) were also included. Speech stimuli consisted of 200 Japanese meaningful sentences. In interrupted stimuli, speech segments were alternated with either silent gaps or pink noise bursts. The noise bursts had a level of - 10, 0 or + 10 dB relative to the speech level. Segment duration varied from 20 to 160 ms for ILTR sentences, but was fixed at 160 ms for I sentences. At segment durations between 40 and 80 ms, severe reductions in intelligibility were observed for ILTR sentences, compared with LTR sentences. A substantial improvement in intelligibility (30-33%) was observed when 40-ms silent gaps in ILTR were replaced with 0- and + 10-dB noise. Noise with a level of - 10 dB had no effect on the intelligibility. These findings show that the combined effects of interruptions and temporal reversal of speech segments on intelligibility are greater than the sum of each individual effect. The results also support the idea that illusory continuity induced by high-level noise bursts improves the intelligibility of ILTR and I sentences.

Development of singleton consonants in French-speaking children with typical versus protracted phonological development: The influence of word length, word shape and stress.

PURPOSE: To provide preliminary reference data for singleton consonant development in children with typical development (TD) versus protracted phonological development (PPD) for Manitoba Canadian French, a language with an uncommon stress pattern ("iambic" or "right-headed"). Following a nonlinear perspective, singleton consonants were examined both as segments and in terms of the structure of words. Higher match levels for consonants were expected in shorter versus longer words and in stressed versus unstressed syllables. A larger effect was expected in children with PPD than those with TD. METHOD: Participants included 20 TD children and 12 with PPD aged 2 to 4 years from Manitoba, Canada. Single words were digitally recorded by trained speech-language pathologists, transcribed by native French speakers and analysed with Phon 3.0. RESULT: Friedman and Wilcoxon Signed Rank tests revealed that children with PPD had significantly more mismatches than TD children, especially in contexts of unstressed syllables in multisyllabic words. The most common mismatch ("error") patterns were consonant substitution, consonant deletion and syllable deletion. CONCLUSION: Word length and stress were found to influence consonant development within French, similar to findings in languages with left-headed or trochaic stress. Clinically, the findings underscore the relevance of considering the child's entire phonological system for identification of strengths and needs in assessment and intervention.

The auditory organization of complex sounds.

This chapter reviews the existing evidence on the auditory processes that are responsible for the formation of auditory percepts in natural listening situations ('the auditory scene'). The formation of the perceptual attributes of auditory events is explained as the result of the interaction of two types of auditory grouping processes, general-purpose and schema-based processes. A further distinction is made between attribute-specific and categorical schemas. After discussing the formation of perceptual attributes and of the timbre of familiar sounds, the chapter explores current knowledge on how the brain builds perceptual representations of simultaneous auditory events and of sequences of auditory events. The nature of auditory scene analysis processes and of their interactions is discussed, and a tentative interactive model is proposed as a framework for future research.

New cochlear implant coding strategy for tonal language speakers.

Accurate pitch perception on the basis of fundamental frequency patterns is essential for the processing of lexical tones in tonal languages such as Cantonese. Speech intelligibility in Cantonese-speaking CI recipients was compared using current signal processing strategies, which typically result in poor pitch perception, and a new strategy, known as the multi-channel envelope modulation (MEM) strategy, was designed to enhance temporal periodicity cues to the fundamental frequency. Performance of nine postlingually hearing-impaired adult cochlear implant users was measured twice using each strategy, initially after a four week trial, and again after two weeks of use with each strategy. Speech intelligibility in speech-spectrum shaped noise was measured using the Cantonese hearing in noise test. A fixed noise level of 65 dB A was used and the signal-to-noise ratios were fixed at either +10, +15, or +20 dB, depending on the baseline performance of individual subjects using the clinical processor. Self-reported benefit in 18 listening situations and overall preference for strategies were obtained at the end of these trial periods. Results showed poorer speech intelligibility with CIS while results obtained using ACE and MEM were comparable. Unfamiliar place coding might have contributed to poorer performance using CIS. Self-reported benefit across strategies did not differ in most listening situations. Participants preferred ACE for listening overall in daily situations, and a few preferred MEM in noise. Whilst the results did not demonstrate any advantages for speech recognition in noise when using MEM compared to ACE, no degradation in performance was observed. This implies that the form of processing employed by MEM retains similar segmental information to that provided by ACE and that potentially, future variations/optimizations of MEM may lead to some improvement in tone perception.

Can spectro-temporal complexity explain the autistic pattern of performance on auditory tasks?

To test the hypothesis that level of neural complexity explain the relative level of performance and brain activity in autistic individuals, available behavioural, ERP and imaging findings related to the perception of increasingly complex auditory material under various processing tasks in autism were reviewed. Tasks involving simple material (pure tones) and/or low-level operations (detection, labelling, chord disembedding, detection of pitch changes) show a superior level of performance and shorter ERP latencies. In contrast, tasks involving spectrally- and temporally-dynamic material and/or complex operations (evaluation, attention) are poorly performed by autistics, or generate inferior ERP activity or brain activation. Neural complexity required to perform auditory tasks may therefore explain pattern of performance and activation of autistic individuals during auditory tasks.

An acoustic and perceptual study of final stops produced by profoundly hearing impaired adolescents.

PURPOSE: This study investigated formant frequencies for their role as acoustic and perceptual correlates to the place of articulation of Cantonese final stops produced by profoundly hearing impaired speakers. METHOD: Speakers were 10 Cantonese adolescents (mean age=13;5 [years;months]) who were profoundly hearing impaired (HI). Control speakers were 10 adolescents (mean age=13;5) with normal hearing. Stimuli were Cantonese words that were minimally contrastive in place of final stops (/p, t, k/). Listeners were 10 final-year speech therapy students. The frequencies of F1, F2, and F3 were measured at the middle, 40 ms before the end, and at the end of the vocalic segments. RESULTS: Control speakers distinguished place contrasts through formant frequency differences at the end positions of the vowels. HI speakers produced final stops with missing formant transitions and neutralized vowels preceding final stops. Listeners relied on F2 transition cues for stops produced by control speakers, whereas F1 and F3 transition cues were used for stops produced by HI speakers. CONCLUSIONS: Formant frequencies of final stops produced by HI speakers showed reduced place distinction. When listeners identified the place of final stops produced by HI speakers, they relied on formant frequency cues that were different from those used for stops produced by control speakers.

The interaction of ambient frequency and feature complexity in the diphthong errors of children with phonological disorders.

This study examined the interaction of ambient frequency and feature complexity in the diphthong errors produced by Cantonese-speaking children with phonological disorders. A total of 611 diphthongs produced by 13 Cantonese-speaking children with speech disorders were subjected to perceptual analysis. The percentage accuracy of production and error patterns was examined. Perceptual analysis showed that /(see text)i/ and /ui/ were most frequently in error, whereas /ei/, /ou/, and /(see text)u/ were least frequently in error. Diphthong errors (usually diphthong reduction) arise as a function of both ambient frequency and feature complexity. The combination of ambient frequency and feature complexity yields a complexity metric reflecting accuracy of production. Treatment guidelines include consideration of three basic factors: ambient frequency, feature complexity, and error patterns.

Effects of culture on musical pitch perception.

The strong association between music and speech has been supported by recent research focusing on musicians' superior abilities in second language learning and neural encoding of foreign speech sounds. However, evidence for a double association--the influence of linguistic background on music pitch processing and disorders--remains elusive. Because languages differ in their usage of elements (e.g., pitch) that are also essential for music, a unique opportunity for examining such language-to-music associations comes from a cross-cultural (linguistic) comparison of congenital amusia, a neurogenetic disorder affecting the music (pitch and rhythm) processing of about 5% of the Western population. In the present study, two populations (Hong Kong and Canada) were compared. One spoke a tone language in which differences in voice pitch correspond to differences in word meaning (in Hong Kong Cantonese, /si/ means 'teacher' and 'to try' when spoken in a high and mid pitch pattern, respectively). Using the On-line Identification Test of Congenital Amusia, we found Cantonese speakers as a group tend to show enhanced pitch perception ability compared to speakers of Canadian French and English (non-tone languages). This enhanced ability occurs in the absence of differences in rhythmic perception and persists even after relevant factors such as musical background and age were controlled. Following a common definition of amusia (5% of the population), we found Hong Kong pitch amusics also show enhanced pitch abilities relative to their Canadian counterparts. These findings not only provide critical evidence for a double association of music and speech, but also argue for the reconceptualization of communicative disorders within a cultural framework. Along with recent studies documenting cultural differences in visual perception, our auditory evidence challenges the common assumption of universality of basic mental processes and speaks to the domain generality of culture-to-perception influences.

Enhanced pure-tone pitch discrimination among persons with autism but not Asperger syndrome.

Persons with Autism spectrum disorders (ASD) display atypical perceptual processing in visual and auditory tasks. In vision, Bertone, Mottron, Jelenic, and Faubert (2005) found that enhanced and diminished visual processing is linked to the level of neural complexity required to process stimuli, as proposed in the neural complexity hypothesis. Based on these findings, Samson, Mottron, Jemel, Belin, and Ciocca (2006) proposed to extend the neural complexity hypothesis to the auditory modality. They hypothesized that persons with ASD should display enhanced performance for simple tones that are processed in primary auditory cortical regions, but diminished performance for complex tones that require additional processing in associative auditory regions, in comparison to typically developing individuals. To assess this hypothesis, we designed four auditory discrimination experiments targeting pitch, non-vocal and vocal timbre, and loudness. Stimuli consisted of spectro-temporally simple and complex tones. The participants were adolescents and young adults with autism, Asperger syndrome, and typical developmental histories, all with IQs in the normal range. Consistent with the neural complexity hypothesis and enhanced perceptual functioning model of ASD (Mottron, Dawson, Soulières, Hubert, & Burack, 2006), the participants with autism, but not with Asperger syndrome, displayed enhanced pitch discrimination for simple tones. However, no discrimination-thresholds differences were found between the participants with ASD and the typically developing persons across spectrally and temporally complex conditions. These findings indicate that enhanced pure-tone pitch discrimination may be a cognitive correlate of speech-delay among persons with ASD. However, auditory discrimination among this group does not appear to be directly contingent on the spectro-temporal complexity of the stimuli.

The perception of lexical tone contrasts in Cantonese children with and without specific language impairment (SLI).

PURPOSE: This study examined the perception of fundamental frequency (f0) patterns by Cantonese children with and without specific language impairment (SLI). METHOD: Participants were 14 five-year-old children with SLI, and 14 age-matched (AM) and 13 four-year-old vocabulary-matched (VM) controls. The children identified a word from familiar word pairs that illustrated the 8 minimally contrastive pairs of the 6 lexical tones. They discriminated the f0 patterns within contrastive tonal pairs in speech and nonspeech stimuli. RESULTS: In tone identification, the SLI group performed worse than the AM group but not the VM group. In tone discrimination, the SLI group did worse than the AM group on 2 contrasts and showed a nonsignificant trend of poorer performance on all contrasts combined. The VM group generally did worse than the AM group. There were no group differences in discrimination performance between speech and nonspeech stimuli. No correlation was found between identification and discrimination performance. Only the normal controls showed a moderate correlation between vocabulary scores and performance in the 2 perception tasks. CONCLUSION: The SLI group's poor tone identification cannot be accounted for by vocabulary knowledge alone. The group's tone discrimination performance suggests that some children with SLI have a deficit in f0 processing.

Effect of listener training on perceptual judgement of hypernasality.

Reliable perceptual judgement is important for documenting the severity of hypernasality, but high reliability can be difficult to obtain. This study investigated the effect of practice and feedback on intra-judge and inter-judge reliability of hypernasality judgements. The judges were 36 speech-language therapy students, who were randomly assigned to three groups for training: (1) Exposure (simple exposure to hypernasal speech samples), (2) Practice-only (practice with hypernasality judgements without feedback), and (3) Practice-Feedback (practice with hypernasality judgements with feedback). After training, the judges rated hypernasality in non-nasal sentences produced by 20 speakers with hypernasality and two normal speakers, using direct magnitude estimation. Both practice groups showed fair-to-good inter-judge reliability for rating the female samples: had more listeners who showed significant intra-judge reliability, and had significantly larger range of hypernasality ratings than the exposure group. To conclude, practice (with or without feedback) is useful for improving the reliability of hypernasality ratings.

An acoustic and perceptual study of initial stops produced by profoundly hearing impaired adolescents.

This study investigated the role of Voice Onset Time (VOT) as perceptual cue to the aspiration contrast of Cantonese initial stops produced by adolescent profoundly hearing impaired speakers. Speakers with normal hearing signalled the aspiration contrast through VOT differences. Hearing impaired speakers produced initial stops with no significant VOT differences between aspirated and unaspirated stops; the accuracy of perception were above chance level for unaspirated stops but were below chance level for aspirated stops. Discriminant analysis conducted on data from a perceptual task showed that listeners with normal hearing relied on VOT cue for aspiration contrast of initial stops produced by control speakers. By contrast, stops produced by the hearing impaired speakers were not distinguished by listeners on the basis of VOT in that listeners were able to rely on VOT as a perceptual cue only to unaspirated stops, but not to aspirated stops.