Perception Of Stop Consonants Research Articles

The effect of native language and bilingualism on multimodal perception in speech: A study of audio-aerotactile integrationa).

Previous studies of speech perception revealed that tactile sensation can be integrated into the perception of stop consonants. It remains uncertain whether such multisensory integration can be shaped by linguistic experience, such as the listener's native language(s). This study investigates audio-aerotactile integration in phoneme perception for English and French monolinguals as well as English-French bilingual listeners. Six step voice onset time continua of alveolar (/da/-/ta/) and labial (/ba/-/pa/) stops constructed from both English and French end points were presented to listeners who performed a forced-choice identification task. Air puffs were synchronized to syllable onset and randomly applied to the back of the hand. Results show that stimuli with an air puff elicited more "voiceless" responses for the /da/-/ta/ continuum by both English and French listeners. This suggests that audio-aerotactile integration can occur even though the French listeners did not have an aspiration/non-aspiration contrast in their native language. Furthermore, bilingual speakers showed larger air puff effects compared to monolinguals in both languages, perhaps due to bilinguals' heightened receptiveness to multimodal information in speech.

The influences of forward context on stop-consonant perception: The combined effects of contrast and acoustic cue activation?

The perception of the /da/-/ga/ series, distinguished primarily by the third formant (F3) transition, is affected by many nonspeech and speech sounds. Previous studies mainly investigated the influences of context stimuli with frequency bands located in the F3 region and proposed the account of spectral contrast effects. This study examined the effects of context stimuli with bands not in the F3 region. The results revealed that these non-F3-region stimuli (whether with bands higher or lower than the F3 region) mainly facilitated the identification of /ga/; for example, the stimuli (including frequency-modulated glides, sine-wave tones, filtered sentences, and natural vowels) in the low-frequency band (500-1500 Hz) led to more /ga/ responses than those in the low-F3 region (1500-2500 Hz). It is suggested that in the F3 region, context stimuli may act through spectral contrast effects, while in non-F3 regions, context stimuli might activate the acoustic cues of /g/ and further facilitate the identification of /ga/. The combination of contrast and acoustic cue effects can explain more results concerning the forward context influences on the perception of the /da/-/ga/ series, including the effects of non-F3-region stimuli and the imbalanced influences of context stimuli on /da/ and /ga/ perception.

The Temporal Dynamics of Stop Consonant Perception: Evidence from Context Effects.

Empirical evidence and theoretical models suggest that phonetic category perception involves two stages of auditory and phonetic processing. However, few studies examined the time course of these two processing stages. With brief stop consonant segments as context stimuli, this study examined the temporal dynamics of stop consonant perception by varying the inter-stimulus interval between context and target stimuli. The results suggest that phonetic category activation of stop consonants may appear before 100 ms of processing time. Furthermore, the activation of phonetic categories resulted in contrast context effects on identifying the target stop continuum; the auditory processing of stop consonants resulted in a different context effect from those caused by phonetic category activation. The findings provide further evidence for the two-stage model of speech perception and reveal the time course of auditory and phonetic processing.

Vowel Context Effect on the Perception of Stop Consonants in Malayalam and Its Role in Determining Syllable Frequency.

Background and ObjectivesThe study investigated vowel context effects on the perception of stop consonants in Malayalam. It also probed into the role of vowel context effects in determining the frequency of occurrence of various consonant-vowel (CV) syllables in Malayalam.Subjects and MethodsThe study used a cross-sectional pre-experimental post-test only research design on 30 individuals with normal hearing, who were native speakers of Malayalam. The stimuli included three stop consonants, each spoken in three different vowel contexts. The resultant nine syllables were presented in original form and five gating conditions. The consonant recognition in different vowel contexts of the participants was assessed. The frequency of occurrence of the nine target syllables in the spoken corpus of Malayalam was also systematically derived.ResultsThe consonant recognition score was better in the /u/ vowel context compared with /i/ and /a/ contexts. The frequency of occurrence of the target syllables derived from the spoken corpus of Malayalam showed that the three stop consonants occurred more frequently with the vowel /a/ compared with /u/ and /i/.ConclusionsThe findings show a definite vowel context effect on the perception of the Malayalam stop consonants. This context effect observed is different from that in other languages. Stop consonants are perceived better in the context of /u/ compared with the /a/ and /i/ contexts. Furthermore, the vowel context effects do not appear to determine the frequency of occurrence of different CV syllables in Malayalam.

Learning Challenging L2 Sounds Via Computer Training: High-Variability Perceptual Training for Children and Adults

ABSTRACT Do learners of a second language (L2) need frequent contact with native speakers of that language in order to master its phonology? What if they hear audio recordings of native speakers and receive immediate corrective feedback about their perception? We used a randomized controlled experiment with 135 Chinese speakers (with English as their L2) to examine whether a high-variability perceptual training (HVPT) paradigm might enhance the perception of challenging contrasts between English voiced and voiceless stop consonants. Learners in all the age groups tested – middle childhood, early adolescence, and young adulthood – showed enhanced perception of English stop consonants after 20 five-minute training sessions conducted across 4 to 6 weeks, based on audio-recorded input coupled with corrective feedback. The training benefits were maintained at the one-month follow-up. Our results suggest that HVPT using audio-recordings of native speakers can be an affordable and useful language enrichment to supplement live interaction with native speakers, for L2 learners of a wide age range.

Silence-cued stop perception: Split decisions

Bastian, Eimas, & Liberman (1961) found that listeners heard a [p] when a silence of more than 50ms was inserted between the [s] and the [l] in a recording of the word slit. It has long been known that silence is an important cue in stop consonant perception. Nevertheless, it is surprising that a short interval of silence can substitute for something as acoustically and articulatorily complex as a phoneme. In the present work, we replicate and expand upon this study to further examine the phenomenon of silence-cued stop perception. We demonstrate the ‘Split Effect’ in a previously unexplored set of environments, analyze factors that contribute to the identity of silence-cued stops, and lay the groundwork for further investigation of the acoustic and non-acoustic factors that contribute to this perceptual illusion. Our study demonstrates an experimental paradigm for studying the genesis of such effects synchronically and in a controlled setting.

An analysis of the perception of stop consonants in bilinguals and monolinguals in different phonetic contexts: A range-based language cueing approach.

Bilinguals' observed perceptual shift across language contexts for shared acoustic properties between their languages supports the idea that bilinguals, but not monolinguals, develop two phonemic representations for the same acoustic property. This phenomenon is known as the double phonemic boundary. This investigation replicated previous findings of bilinguals' double phonemic boundary across a series of go/no-go tasks while controlling for known confounding effects in speech perception (i.e., contrast effects) and differences in resource allocation between bilinguals and monolinguals (i.e., left-hand or right-hand response). Using a range-base language cueing approach, we designed 2 experiments. The first experiment tested whether a voice onset time (VOT) range representative of either Spanish or English phonetic categories can cue bilinguals, but not monolinguals, to use language-specific perceptual routines. The second experiment tested a VOT range with a mixture of Spanish and English phonetic categories to determine whether directing attention to a specific phonetic category can disambiguate the competition of the nonattended category. The results for Experiment 1 showed that bilinguals can rely on the distributional patterns of their native phonetic categories to activate specific language modes. Experiment 2 showed that attention can change the weight given to a native phonetic distinction. However, this process is restricted by the internal phonetic composition of the native language(s).

Revisiting Perception–Production Relationships: Exploring a New Approach to Investigate Perception as a Time‐Varying Predictor

AbstractModels of L2 pronunciation learning have hypothesized that accurate speech perception promotes accurate speech production. This claim can be evaluated longitudinally by examining the extent to which changes in stop consonant perception predict changes in stop consonant production. Taking a time‐sensitive view of the perception–production link, this study used longitudinal data to analyze perception as a time‐varying predictor of production accuracy. Mixed‐effects models were fit to oddity, delayed word repetition, and picture description tasks to examine how participants’ perception and production changed over time. Oddity task perception data were then decomposed into their between‐ and within‐subjects components and integrated into the delayed repetition and picture description production models. Surprisingly, only the between‐subjects predictors reached significance, and the strength of the perception–production link varied across production tasks and target phones. The methods used have implications for future research on perception–production links.

Statistical and acoustic effects on the perception of stop consonants in Kaqchikel (Mayan)

This paper investigates the relationship between speech perception and linguistic experience in Kaqchikel, a Guatemalan Mayan language. Our empirical focus is the perception of plain, ejective, and implosive stops. Drawing on an AX discrimination task, a corpus of spoken Kaqchikel, and a text corpus, we make two claims. First, we argue that speech perception is mediated by phonemic representations which include acoustic detail drawn from prior phonetic experience, as in Exemplar Theory. Second, segmental distributions also condition speech perception: The perceptual distinctiveness of a pair of phonemes is affected by their functional load and relative contextual predictability. These top-down factors influence phoneme discrimination even at relatively fast response times. We take this result as evidence that distributional factors like functional load may affect speech perception by shaping perceptual tuning during linguistic development. This study replicates and extends some key findings in speech perception in the context of a language (Kaqchikel) which is structurally and sociolinguistically different from the majority languages (like English) which have served as the basis of most work in the speech perception literature. At the practical level, our research illustrates methods for conducting corpus-based laboratory phonology with lesser-studied and under-resourced languages.

The relative contribution of visual cues and acoustic enhancement strategies in improving speech perception of individuals with auditory neuropathy spectrum disorders

Background and Objectives: The present study aimed to assess the relative benefits of visual cue supplementation and acoustic enhancement in improving speech perception of individuals with Auditory Neuropathy Spectrum Disorders (ANSD). Methods: The study utilized repeated measure research design. Based on the purposive sampling 40 participants with ANSD were selected. They were assessed for their speech identification of monosyllables in auditory only (A), visual only (V), and auditory-visual (AV) modalities. In the A and AV modalities, the perception of the primary, temporally enhanced, and spectrally enhanced syllables were assessed in quiet as well as 0 dB signal to noise ratio (SNR) conditions. The identification scores were compared across modalities, stimuli, and conditions to derive the relative benefits of visual cues and acoustic enhancement on speech perception of individuals with ANSD. Results: The group data showed a significant effect of modality with the mean identification score being the maximum in AV modality. This was true both in quiet and 0 dB SNR. The mean identification scores in quiet were significantly higher compared to that in 0 dB SNR. However, acoustic enhancement of speech did not significantly enhance speech perception. When acoustic enhancement and visual cues were simultaneously provided, speech perception was determined only by visual cues. The evidence from individual data showed that most of the individuals benefit from AV modality. Conclusions: The findings indicate that both auditory and visual modality needs to be facilitated in ANSD to enhance speech perception. The acoustic enhancements in the current form have negligible influence. However, the inference shall be restricted to the perception of stop consonants.

Infant-directed speech in English and Spanish: Assessments of monolingual and bilingual caregiver VOT

It has been shown that monolingual caregivers exaggerate acoustic speech cues in infant-directed speech (IDS), but less is known about the characteristics of IDS in late second-language (L2) bilingual caregivers. Furthermore, there is inconsistency in the literature regarding voice onset time (VOT) of stop consonants in IDS. The present study explores VOT of English and Spanish stops in English monolingual and Spanish-dominant bilingual caregivers, in infant- versus adult-directed speech registers. Both monolinguals and bilinguals exaggerate VOT in IDS; however, different patterns are noted across consonant type and language context. Also, bilinguals produced English stops with Spanish-like and English-like properties, depending upon their L2-proficiency. The characteristics of late-L2 Spanish–English bilingual IDS may create a complex phonetic environment for infants, which may in turn affect the perception and later production of stop consonants in dual language-learning infants.

Between-Frequency and Between-Ear Gap Detections and Their Relation to Perception of Stop Consonants.

The objective of this study was to examine the hypothesis that between-channel gap detection, which includes between-frequency and between-ear gap detection, and perception of stop consonants, which is mediated by the length of voice-onset time (VOT), share common mechanisms, namely relative-timing operation in monitoring separate perceptual channels. The authors measured gap detection thresholds and identification functions of /ba/ and /pa/ along VOT in 49 native young adult Japanese listeners. There were three gap detection tasks. In the between-frequency task, the leading and trailing markers differed in terms of center frequency (Fc). The leading marker was a broadband noise of 10 to 20,000 Hz. The trailing marker was a 0.5-octave band-passed noise of 1000-, 2000-, 4000-, or 8000-Hz Fc. In the between-ear task, the two markers were spectrally identical but presented to separate ears. In the within-frequency task, the two spectrally identical markers were presented to the same ear. The /ba/-/pa/ identification functions were obtained in a task in which the listeners were presented synthesized speech stimuli of varying VOTs from 10 to 46 msec and asked to identify them as /ba/ or /pa/. The between-ear gap thresholds were significantly positively correlated with the between-frequency gap thresholds (except those obtained with the trailing marker of 4000-Hz Fc). The between-ear gap thresholds were not significantly correlated with the within-frequency gap thresholds, which were significantly correlated with all the between-frequency gap thresholds. The VOT boundaries and slopes of /ba/-/pa/ identification functions were not significantly correlated with any of these gap thresholds. There was a close relation between the between-ear and between-frequency gap detection, supporting the view that these two types of gap detection share common mechanisms of between-channel gap detection. However, there was no evidence for a relation between the perception of stop consonants and the between-frequency/ear gap detection in native Japanese speakers.

Final Stop Consonant Perception in Children with Speech Sound Disorders

ë°°ê²½ 및 ëª©ì : ë§ì†Œë¦¬ìž¥ì• ì˜ 원인 중 하나로서 말지각 ëŠ¥ë ¥ìƒì˜ 결함이 ì§€ì†ì ìœ¼ë¡œ ë ¼ì˜ë˜ì–´ì™”ë‹¤. 본 연구에서는 일반아동과 비교해서 ë§ì†Œë¦¬ìž¥ì• ì•„ë™ì´ ì¢ ì„±íŒŒì—´ìŒì˜ ìŒí–¥í•™ì  단서를 ì™„ì „ížˆ ì œê³µí•˜ê±°ë‚˜ 일부를 ì‚­ì œí•˜ì—¬ ì œê³µí•˜ëŠ” 조건에서 ì¢ ì„±íŒŒì—´ìŒì— 대한 ì§€ê°ë ¥ì´ ì–´ë– í•œì§€ ì‚´íŽ´ë³´ê³ ìž 하였다. 방법: ë§ì†Œë¦¬ìž¥ì• ì•„ë™ê³¼ 일반 아동 각각 15ëª ì„ 대상으로 두 쌍의 ì¼ìŒì ˆ 단어의 ìŒí–¥í•™ì  ì •ë³´ë¥¼ 모두 ì œê³µí•œ ì „ì²´ì¡°ê±´ê³¼ 어말 ì¢ ì„±ì˜ ì „ì²´ì ì¸ ìŒí–¥í•™ì  구간 끝에서 40 ms와 60 ms씩을 잘라낸 조건을 총 4회씩 ì œì‹œí•˜ì˜€ë‹¤. 아동은 자극어를 ë“£ê³ ì†Œë¦¬ì— 해당하는 그림을 ì§€ì í•˜ì˜€ìœ¼ë©°, 아동의 반응을 d-prime 값으로 변환하여 분석하였다. ê²°ê³¼: 자극어 ‘밥-밭’에서는 ë§ì†Œë¦¬ìž¥ì• ì•„ë™ê³¼ 일반아동 집단 간 ì§€ê°ë ¥ì— ìœ ì˜ë¯¸í•œ 차이가 나타났으며, 집단 내 자극어 ì¡°ê±´(ì „ì²´, -40 ms, -60 ms)에 따른 ì§€ê°ë ¥ì—ë„ ìœ ì˜í•œ 차이가 나타났다. ì¡°ê±´ê³¼ 집단에 따른 상호작용 효과는 ìœ ì˜ë¯¸í•˜ì§€ 않았다. 자극어 ‘목-못’에서는 두 집단 간 ì§€ê°ë ¥ì— ìœ ì˜ë¯¸í•œ 차이가 나타나지 않았으며, 집단 내 자극어 조건에 따른 ì§€ê°ë ¥ì— ìœ ì˜í•œ 차이도 나타나지 않았다. ë ¼ì˜ 및 ê²°ë¡ : 본 연구결과는 일반 아동에 비해 ë§ì†Œë¦¬ìž¥ì• ì•„ë™ì´ ìŒí–¥í•™ì  ì •ë³´ê°€ 일부 ì‚­ì œëœ 조건뿐만 아니라 ìŒí–¥í•™ì  ì •ë³´ê°€ ì™„ì „í•˜ê²Œ ì œì‹œëœ 조건에서도 말소리를 지각하는데 ì–´ë ¤ì›€ì„ 보일 수 있음을 ì œì‹œí•˜ê³ ìžˆë‹¤. 이러한 결과를 바탕으로 말소리 지각 ëŠ¥ë ¥ìƒì˜ 결함으로 인해 말소리 산출상의 ë¬¸ì œê°€ ë‚˜íƒ€ë‚ ìˆ˜ 있음을 ì¶”ë¡ í•´ë³¼ 수 있다. Keywords: ë§ì†Œë¦¬ìž¥ì• , ì¢ ì„±íŒŒì—´ìŒ, 말-ì§€ê°ë ¥, ê²Œì´íŒ ê³¼ì œ, 여분의 ìŒí–¥í•™ì  ì •ë³´

KSZTAŁTOWANIE SIĘ PRZETWARZANIA STRUKTURY CZASOWEJ SYGNAŁU U DZIECI: POMIARY PRZY UŻYCIU BODŹCÓW WERBALNYCH I NIEWERBALNYCH

BackgroundAuditory temporal processing is the ability of the nervous system to detect small variations in the duration of an acoustic stimuli. A substantial body of research is available on the development of various temporal skills, but temporal resolution abilities have not been well investigated in terms of speech and non-speech stimuli. The present study investigates the development of temporal resolution abilities in children.Material and MethodsA normative cross-sectional research design was adopted by administering a set of psychoacoustic tests involving both speech and non-speech stimuli. Six groups of 20 children each, aged 6–12 years, with a 1-year interval between each age group, were tested and the results were compared with those of 20 adults.ResultsThe results revealed generally poorer performance of children on the entire test battery. Temporal modulation transfer function test scores, word recognition scores, and categorical perception of stop consonants matured by about 10–11 years of age. Gap detection test and time compressed speech test results showed maturation at around 8–9 years of age, whereas temporal change detection continued to mature even for the second decade of life.ConclusionsOverall, maturation of temporal processing skills is reached by 10–11 years of age. This information is relevant when evaluating children with various processing disorders, and should also be considered when developing various assessment and rehabilitation protocols for children with special abilities.

4-6세 정상발달아동 및 성인의 종성파열음 지각력 비교

This study aimed to identify the development pattern of final stop consonant perception using the gating task. Sixty-four subjects participated in the study: 16 children aged 4 years, 16 children aged 5 years, 17 children aged 6 years, and 15 adults. One-syllable words with consonant-vowel-consonant(CVC) structure, mokㄱ-motㄱ and papㄱ-patㄱ were used as stimuli in order to remove the redundancy of acoustic cues in stimulus words, 40ms-length (-40ms) and 60ms-length (-60ms) from the entire duration of the final consonant were deleted. Three conditions (the whole word segment, -40ms, -60ms) were used for this speech perception experiment. 48 tokens (4 stimuli conditions trials) in total were provided for participants. The results indicated that 5 and 6 year olds showed final consonant perception similar to adults in stimuli, papㄱ-patㄱ and only the 6-year-old children showed perception similar to adults in stimuli, `mokㄱ-motㄱ. The results suggested that younger typically developing children require more acoustic information to accurately perceive final consonants than older children and adults. Final consonant perception ability may become adult-like around 6 years old. The study provides fundamental data on the development pattern of speech perception in normal developing children, which can be used to compare to those of children with communication disorders.

Impact of Spectrally Asynchronous Delays on Consonant Voicing Perception

A possible voicing cue used to differentiate voiced and voiceless cognate pairs is envelope onset asynchrony (EOA). EOA is the time between the onsets of two frequency bands of energy (in this study one band was high-pass filtered at 3000 Hz, the other low-pass filtered at 350 Hz). This study assessed the perceptual impact of manipulating EOA on voicing perception of initial stop consonants, and whether normal-hearing and hearing-impaired listeners were sensitive to changes in EOA as a cue for voicing. The purpose of this study was to examine the effect of spectrally asynchronous auditory delay on the perception of voicing associated with initial stop consonants by normal-hearing and hearing-impaired listeners. Prospective experimental study comparing the perceptual differences of manipulating the EOA cues for two groups of listeners. Thirty adults between the ages of 21 and 60 yr completed the study: 17 listeners with normal hearing and 13 listeners with mild-moderate sensorineural hearing loss. The participants listened to voiced and voiceless stop consonants within a consonant-vowel syllable structure. The EOA of each syllable was varied along a continuum, and identification and discrimination tasks were used to determine if the EOA manipulation resulted in categorical shifts in voicing perception. In the identification task the participants identified the consonants as belonging to one of two categories (voiced or voiceless cognate). They also completed a same-different discrimination task with the same set of stimuli. Categorical perception was confirmed with a d-prime sensitivity measure by examining how accurately the results from the identification task predicted the discrimination results. The influence of EOA manipulations on the perception of voicing was determined from shifts in the identification functions and discrimination peaks along the EOA continuum. The two participant groups were compared in order to determine the impact of EOA on voicing perception as a function of syllable and hearing status. Both groups of listeners demonstrated a categorical shift in voicing perception with manipulation of EOA for some of the syllables used in this study. That is, as the temporal onset asynchrony between low- and high-frequency bands of speech was manipulated, the listeners' perception of consonant voicing changed between voiced and voiceless categories. No significant differences were found between listeners with normal hearing and listeners with hearing loss as a result of the EOA manipulation. The results of this study suggested that both normal-hearing and hearing-impaired listeners likely use spectrally asynchronous delays found in natural speech as a cue for voicing distinctions. While delays in modern hearing aids are less than those used in this study, possible implications are that additional asynchronous delays from digital signal processing or open-fitting amplification schemes might cause listeners with hearing loss to misperceive voicing cues.

Reading fluency and speech perception speed of beginning readers with persistent reading problems: the perception of initial stop consonants and consonant clusters

This study investigated the role of speech perception accuracy and speed in fluent word decoding of reading disabled (RD) children. A same-different phoneme discrimination task with natural speech tested the perception of single consonants and consonant clusters by young but persistent RD children. RD children were slower than chronological age (CA) controls in recognizing identical sounds, suggesting less distinct phonemic categories. In addition, after controlling for phonetic similarity Tallal’s (Brain Lang 9:182–198, 1980) fast transitions account of RD children’s speech perception problems was contrasted with Studdert-Kennedy’s (Read Writ Interdiscip J 15:5–14, 2002) similarity explanation. Results showed no specific RD deficit in perceiving fast transitions. Both phonetic similarity and fast transitions influenced accurate speech perception for RD children as well as CA controls.

Effects of Hearing Loss and Spectral Shaping on Identification and Neural Response Patterns of Stop-Consonant Stimuli in Young Adults

The primary purpose of this study was to more clearly define the effects of hearing loss, separate from age, on perception, and neural response patterns of dynamic spectral cues. To do this, the study was designed to determine whether (1) hearing loss affects the neural representation and/or categorical perception of stop-consonant stimuli among young adults and (2) spectrally shaped amplification aimed at increasing the audibility of the F2 formant transition cue reduces any effects of hearing loss. It was predicted that (1) young adults with hearing loss would differ from young adults with normal hearing in their behavioral and neural responses to stop-consonant stimuli and (2) enhancing the audibility of the F2 formant transition cue relative to the rest of the stimulus would not overcome the effects of hearing loss on behavioral performance or neural response patterns. Behavioral identification and neural response patterns of stop-consonant stimuli varying along the /b-d-g/ place-of-articulation continuum were measured from seven young adults with mild-to-moderate hearing impairment (mean age = 21.4 yr) and compared with responses from 11 young adults with normal hearing (mean age = 27 yr). Psychometric functions and N1-P2 cortical-evoked responses were evoked by consonant-vowel (CV) stimuli without (unshaped) and with (shaped) frequency-dependent amplification that enhanced F2 relative to the rest of the stimulus. Behavioral identification and neural response patterns of stop-consonant CVs differed between the two groups. Specifically, to the unshaped stimuli, listeners with hearing loss tended to make low-frequency judgments more often (more /b/, fewer /g/) than listeners with normal hearing when categorizing along the /b-d-g/ continuum. Additionally, N1 amplitudes were larger and P2 latencies were longer to all phonemes in young adults with hearing impairment versus normal hearing. Enhancing the audibility of the F2 transition cue with spectrally shaped amplification did not alter the neural representation of the stop-consonant CVs in the young listeners with hearing loss. It did modify categorical perception such that listeners with hearing loss tended to make high-frequency judgments more often (more /g/, fewer /b/). However, shaping the stimuli did not make their psychometric functions more like those of the normal controls. Instead, young adults with hearing loss went from one extreme (low-frequency judgments with unshaped stimuli) to the other (high-frequency judgments with shaped stimuli), whereas judgments from the normal controls were more balanced. Hearing loss, separate from aging, seems to negatively impact identification and neural representation of time-varying spectral cues like the F2 formant transition. Enhancing the audibility of the F2 formant transition cue relative to the rest of the stimulus does not overcome the effects of hearing loss on behavioral performance or neural response patterns in young adults. Thus, the deleterious effects of hearing loss on stop-consonant perception along the place-of-articulation continuum may not only be due solely to decreased audibility but also due to improper coding by residual neurons, resulting in distortion of the time-varying spectral cue. This may explain, in part, why amplification cannot completely compensate for the effects of sensorineural hearing loss.

Spectral Tilt Change in Stop Consonant Perception by Listeners With Hearing Impairment

To evaluate how perceptual importance of spectral tilt is altered when formant information is degraded by sensorineural hearing loss. Eighteen listeners with mild to moderate hearing impairment (HI listeners) and 20-23 listeners with normal hearing (NH listeners) identified synthesized stimuli that varied in second formant (F(2)) frequency and spectral tilt. Experiments 1 and 2 examined utterance-initial stops (/ba/ and /da/), and Experiments 3 and 4 examined medial stops (/aba/ and /ada/). Spectral tilt was manipulated at either consonant onset (Experiments 1 and 3), vowels (Experiments 2 and 4), or both (Experiment 5). Regression analyses revealed that HI listeners weighted F(2) substantially less than NH listeners. There was no difference in absolute tilt weights between groups. However, HI listeners emphasized tilt as much as F(2) for medial stops. NH listeners weighted tilt primarily when F(2) was ambiguous, whereas HI listeners weighted tilt significantly more than NH listeners on unambiguous F(2) endpoints. Attenuating changes in spectral tilt can be as deleterious as taking away F(2) information for HI listeners. Recordings through a wide dynamic range compression hearing aid show compromised changes in spectral tilt, compressed in range by up to 50%.

Natural Boundaries in Gap Detection are Related to Categorical Perception of Stop Consonants

The hypothesis that a natural auditory psychophysical discontinuity contributes to a perceptual category boundary between voiced and voiceless English stop consonants was examined. The relationships between voice onset time (VOT) phonetic boundary and gap-detection thresholds for conditions in which the sounds delimiting the gap were acoustically identical or different were examined in 18 native young adult English speakers. It was specifically hypothesized that between-channel gap-detection thresholds, in contrast to within-channel gap thresholds, would be better predictors of categorical VOT values for listeners. The stimuli used in the between-channel gap-detection task were designed such that dissimilar leading and trailing markers of the gap approximated a stop burst and a following vowel, both in terms of temporal and spectral relationships, while being devoid of phonetic identity. The stimuli used to examine the VOT measure were synthesized bilabial stop syllables in a continuum ranging from /ba/ to /pa/. Statistically significant larger gap thresholds were found for the between-channel conditions than for the within-channel condition (p < 0.05). The center frequency of the trailing marker affected the between-channel gap thresholds with the thresholds improving as the center frequency increased (p < 0.05). Statistically significant positive correlations and predictive linear relations were found between VOT phonetic boundaries and between-channel gap thresholds (p < 0.05) but not within-channel gap thresholds (p > 0.05). A relationship between the phonetic boundary of voiced-voiceless speech sounds and the auditory temporal resolution task of detecting gaps placed within dissimilar markers, regardless of the center frequency of the trailing marker noise burst, was demonstrated. Detection of gaps between different nonspeech acoustic markers and categorical perception of VOT seems to share the same underlying perceptual timing mechanisms in native English speakers.