Comparing identification of standardized and regionally valid vowels

Relative Contributions of Social, Contextual, and Lexical Factors in Speech Processing

This exploratory study examined the simultaneous interactions and relative contributions of bottom-up social information (regional dialect, speaking style), top-down contextual information (semantic predictability), and the internal dynamics of the lexicon (neighborhood density, lexical frequency) to lexical access and word recognition. Cross-modal matching and intelligibility in noise tasks were conducted with a community sample of adults at a local science museum. Each task featured one condition in which keywords were presented in isolation and one condition in which they were presented within a multiword phrase. Lexical processing was slower and more accurate when keywords were presented in their phrasal context, and was both faster and more accurate for auditory stimuli produced in the local Midland dialect. In both tasks, interactions were observed among stimulus dialect, speaking style, semantic predictability, phonological neighborhood density, and lexical frequency. These interactions revealed that bottom-up social information and top-down contextual information contribute more to speech processing than the internal dynamics of the lexicon. Moreover, the relatively stronger bottom-up social effects were observed in both the isolated word and multiword phrase conditions, suggesting that social variation is central to speech processing, even in non-interactive laboratory tasks. At the same time, the specific interactions observed differed between the two experiments, reflecting task-specific demands related to processing time constraints and signal degradation.

Acoustic Characteristics of Short Vowels by Normal Nepali Young Adults

Introduction

Speech production is the most unique task performed by a human. The speech signals consist of strings of vowels and consonants. Vowels are differentiated based on acoustic characteristics.

Methodology

A total of 50 Nepali students, 25 males and 25 females of the age range 18 to 25 years with no history of voice disorders, flu, neurological disorders, speech, language impairment, and respiratory dysfunction were included in the study. Sustained phonation of five short vowels /a/, /i/, /o/, /u/ and /e/ were used in order to measure the acoustic variables. PRAAT software was used to extract the acoustic parameter of voice; mean pitch, Jitter, RAP, PPQ 5, Shimmer, and APQ 11.

Result

Mean and SD was calculated using SPSS. Mann-Whitney test revealed there was a highly significant difference in all the parameters taken for the study among males and females. However, the females had greater F0, jitter, RAP, PPQ5, shimmer, APQ11 than the males.

Conclusion

Before implementing these norms in clinical set up we must consider that these values are developed for the adults whose L1 is Nepali language and the software used for the establishment of norms was Praat.

Reconsidering commonly used stimuli in speech perception experiments

This paper examines some commonly used stimuli in speech perception experiments and raises questions about their use, or about the interpretations of previous results. The takeaway messages are: 1) the Hillenbrand vowels represent a particular dialect rather than a gold standard, and English vowels contain spectral dynamics that have been largely underappreciated, 2) the /ɑ/ context is very common but not clearly superior as a context for testing consonant perception, 3) /ɑ/ is particularly problematic when testing voice-onset-time perception because it introduces strong confounds in the formant transitions, 4) /dɑ/ is grossly overrepresented in neurophysiological studies and yet is insufficient as a generalized proxy for "speech perception," and 5) digit tests and matrix sentences including the coordinate response measure are systematically insensitive to important patterns in speech perception. Each of these stimulus sets and concepts is described with careful attention to their unique value and also cases where they might be misunderstood or over-interpreted.

Electrophysiological Estimates of the Electrode-Neuron Interface Differ Between Younger and Older Listeners With Cochlear Implants

OBJECTIVES

The primary objective of this study was to quantify differences in evoked potential correlates of spiral ganglion neuron (SGN) density between younger and older individuals with cochlear implants (CIs) using the electrically evoked compound action potential (ECAP). In human temporal bone studies and in animal models, SGN density is the lowest in older subjects and in those who experienced long durations of deafness during life. SGN density also varies as a function of age at implantation and hearing loss etiology. Taken together, it is likely that younger listeners who were deafened and implanted during childhood have denser populations of SGNs than older individuals who were deafened and implanted later in life. In animals, ECAP amplitudes, amplitude growth function (AGF) slopes, and their sensitivity to stimulus interphase gap (IPG) are predictive of SGN density. The authors hypothesized that younger listeners who were deafened and implanted as children would demonstrate larger ECAP amplitudes, steeper AGF slopes, and greater IPG sensitivity than older, adult-deafened and implanted listeners.

DESIGN

Data were obtained from 22 implanted ears (18 individuals). Thirteen ears (9 individuals) were deafened and implanted as children (child-implanted group), and nine ears (9 individuals) were deafened and implanted as adults (adult-implanted group). The groups differed significantly on a number of demographic variables that are implicitly related to SGN density: (1) chronological age; (2) age at implantation; and (3) duration of preimplantation hearing loss. ECAP amplitudes, AGF linear slopes, and thresholds were assessed on a subset of electrodes in each ear in response to two IPGs (7 and 30 µsec). Speech recognition was assessed using a medial vowel identification task.

RESULTS

Compared with the adult-implanted listeners, individuals in the child-implanted group demonstrated larger changes in ECAP amplitude when the IPG of the stimulus was increased from 7 to 30 µsec (i.e., greater IPG sensitivity). On average, child-implanted participants also had larger ECAP amplitudes and steeper AGF linear slopes than the adult-implanted participants, irrespective of IPG. IPG sensitivity for AGF linear slope and ECAP threshold did not differ between age groups. Vowel recognition performance was not correlated with any of the ECAP measures assessed in this study.

CONCLUSIONS

The results of this study support the theory that young CI listeners who were deafened and implanted during childhood may have denser neural populations than older listeners who were deafened and implanted as adults. Potential between-group differences in SGN integrity emphasize a need to investigate optimized CI programming parameters for younger and older listeners.

Sociophonetic trends in studies of Southern U.S. English

Although the U.S. South was usually avoided for phonetic studies in earlier years, phonetic analyses of Southern U.S. English have expanded in numerous directions in recent years. Studies of vocalic variation have dominated the enterprise, with a broad range of studies that have examined the phonetic peculiarities and distribution of variants within the region, the characteristics of particular communities, and the phonetic attributes of African American and Latino groups. However, other phonetic phenomena are finally seeing more study. Several consonantal variables have attracted acoustic analysis. Other studies have focused on intonation and certain timing-related phenomena. Numerous experimental studies have tested the abilities of listeners to identify dialects and a few other perceptual issues. These developments are outlined here, including advancements in segmental, prosodic, and perceptual analyses.

Accent Intelligibility Differences in Noise Across Native and Nonnative Accents: Effects of Talker-Listener Pairing at Acoustic-Phonetic and Lexical Levels

Purpose The intelligibility of an accent strongly depends on the specific talker-listener pairing. To explore the causes of this phenomenon, we investigated the relationship between acoustic-phonetic similarity and accent intelligibility across native (1st language) and nonnative (2nd language) talker-listener pairings. We also used online measures to observe processing differences in quiet. Method English ( n = 16) and Spanish ( n = 16) listeners heard Standard Southern British English, Glaswegian English, and Spanish-accented English in a speech recognition task (in quiet and noise) and an electroencephalogram task (quiet only) designed to assess phonological and lexical processing. Stimuli were drawn from the nonnative speech recognition sentences ( Stringer & Iverson, 2019 ). The acoustic-phonetic similarity between listeners' accents and the 3 accents was calculated using the ACCDIST metric ( Huckvale, 2004 , 2007 ). Results Talker-listener pairing had a clear influence on accent intelligibility. This was linked to the phonetic similarity of the talkers and the listeners, but similarity could not account for all findings. The influence of talker-listener pairing on lexical processing was less clear; the N400 effect was mostly robust to accent mismatches, with some relationship to intelligibility. Conclusion These findings suggest that the influence of talker-listener pairing on intelligibility may be partly attributable to accent similarity in addition to accent familiarity. Online measures also show that differences in talker-listener accents can disrupt processing in quiet even where accents are highly intelligible.

Age-Related Performance on Vowel Identification and the Spectral-temporally Modulated Ripple Test in Children With Normal Hearing and With Cochlear Implants

Children’s performance on psychoacoustic tasks improves with age, but inadequate auditory input may delay this maturation. Cochlear implant (CI) users receive a degraded auditory signal with reduced frequency resolution compared with normal, acoustic hearing; thus, immature auditory abilities may contribute to the variation among pediatric CI users’ speech recognition scores. This study investigated relationships between age-related variables, spectral resolution, and vowel identification scores in prelingually deafened, early-implanted children with CIs compared with normal hearing (NH) children. All participants performed vowel identification and the Spectral-temporally Modulated Ripple Test (SMRT). Vowel stimuli for NH children were vocoded to simulate the reduced spectral resolution of CI hearing. Age positively predicted NH children’s vocoded vowel identification scores, but time with the CI was a stronger predictor of vowel recognition and SMRT performance of children with CIs. For both groups, SMRT thresholds were related to vowel identification performance, analogous to previous findings in adults. Sequential information analysis of vowel feature perception indicated greater transmission of duration-related information compared with formant features in both groups of children. In addition, the amount of F2 information transmitted predicted SMRT thresholds in children with NH and with CIs. Comparisons between the two CIs of bilaterally implanted children revealed disparate task performance levels and information transmission values within the same child. These findings indicate that adequate auditory experience contributes to auditory perceptual abilities of pediatric CI users. Further, factors related to individual CIs may be more relevant to psychoacoustic task performance than are the overall capabilities of the child.

Effects of Lexical Competition and Dialect Exposure on Phonological Priming

A cross-modal lexical decision task was used to explore the effects of lexical competition and dialect exposure on phonological form priming. Relative to unrelated auditory primes, matching real word primes facilitated lexical decision for visual real word targets, whereas competing minimal pair primes inhibited lexical decision. These effects were robust across two English vowel pairs (mid-front and low-front) and for two listener groups (mono-dialectal and multi-dialectal). However, both the most robust facilitation and the most robust inhibition were observed for the mid-front vowel words with few phonological competitors for the mono-dialectal listener group. The mid-front vowel targets were acoustically more distinct than the low-front vowel targets, suggesting that acoustic-phonetic similarity leads to stronger lexical competition and less robust facilitation and inhibition. The multi-dialectal listeners had more prior exposure to multiple different dialects than the mono-dialectal group, suggesting that long-term exposure to linguistic variability contributes to a more flexible processing strategy in which lexical competition extends over a longer period of time, leading to less robust facilitation and inhibition.

Vowel and consonant confusions from spectrally manipulated stimuli designed to simulate poor cochlear implant electrode-neuron interfaces

Suboptimal interfaces between cochlear implant (CI) electrodes and auditory neurons result in a loss or distortion of spectral information in specific frequency regions, which likely decreases CI users' speech identification performance. This study exploited speech acoustics to model regions of distorted CI frequency transmission to determine the perceptual consequences of suboptimal electrode-neuron interfaces. Normal hearing adults identified naturally spoken vowels and consonants after spectral information was manipulated through a noiseband vocoder: either (1) low-, middle-, or high-frequency regions of information were removed by zeroing the corresponding channel outputs, or (2) the same regions were distorted by splitting filter outputs to neighboring filters. These conditions simulated the detrimental effects of suboptimal CI electrode-neuron interfaces on spectral transmission. Vowel and consonant confusion patterns were analyzed with sequential information transmission, perceptual distance, and perceptual vowel space analyses. Results indicated that both types of spectral manipulation were equally destructive. Loss or distortion of frequency information produced similar effects on phoneme identification performance and confusion patterns. Consonant error patterns were consistently based on place of articulation. Vowel confusions showed that perceptions gravitated away from the degraded frequency region in a predictable manner, indicating that vowels can probe frequency-specific regions of spectral degradations.

Dialect Interference in Lexical Processing: Effects of Familiarity and Social Stereotypes

BACKGROUND/AIMS

The current study explored the roles of dialect familiarityand social stereotypes in dialect interference effects in a speeded lexical classification task.

METHODS

Listeners classified the words bad and bed or had and head produced by local Midland and non-local Northern talkers and the words sod and side or rod and ride produced by non-local, non-stereotyped Northern and nonlocal, stereotyped Southern talkers in single- and mixed-talker blocks.

RESULTS

Lexical classification was better for the local dialect than for the non-local dialects, and for the stereotyped non-local dialect than for the non-stereotyped non-local dialect. Dialect interference effects were observed for all three dialects, although the patterns of interference differed. For the local dialect, dialect interference was observed for response times, whereas for the non-local dialects, dialect interference was observed primarily for accuracy.

CONCLUSION

These findings reveal complex interactions between indexical and lexical information in speech processing.

Reducing Channel Interaction Through Cochlear Implant Programming May Improve Speech Perception: Current Focusing and Channel Deactivation

Speech perception among cochlear implant (CI) listeners is highly variable. High degrees of channel interaction are associated with poorer speech understanding. Two methods for reducing channel interaction, focusing electrical fields, and deactivating subsets of channels were assessed by the change in vowel and consonant identification scores with different program settings. The main hypotheses were that (a) focused stimulation will improve phoneme recognition and (b) speech perception will improve when channels with high thresholds are deactivated. To select high-threshold channels for deactivation, subjects’ threshold profiles were processed to enhance the peaks and troughs, and then an exclusion or inclusion criterion based on the mean and standard deviation was used. Low-threshold channels were selected manually and matched in number and apex-to-base distribution. Nine ears in eight adult CI listeners with Advanced Bionics HiRes90k devices were tested with six experimental programs. Two, all-channel programs, (a) 14-channel partial tripolar (pTP) and (b) 14-channel monopolar (MP), and four variable-channel programs, derived from these two base programs, (c) pTP with high- and (d) low-threshold channels deactivated, and (e) MP with high- and (f) low-threshold channels deactivated, were created. Across subjects, performance was similar with pTP and MP programs. However, poorer performing subjects (scoring < 62% correct on vowel identification) tended to perform better with the all-channel pTP than with the MP program (1 > 2). These same subjects showed slightly more benefit with the reduced channel MP programs (5 and 6). Subjective ratings were consistent with performance. These finding suggest that reducing channel interaction may benefit poorer performing CI listeners.

The neural encoding of formant frequencies contributing to vowel identification in normal-hearing listeners

Even though speech signals trigger coding in the cochlea to convey speech information to the central auditory structures, little is known about the neural mechanisms involved in such processes. The purpose of this study was to understand the encoding of formant cues and how it relates to vowel recognition in listeners. Neural representations of formants may differ across listeners; however, it was hypothesized that neural patterns could still predict vowel recognition. To test the hypothesis, the frequency-following response (FFR) and vowel recognition were obtained from 38 normal-hearing listeners using four different vowels, allowing direct comparisons between behavioral and neural data in the same individuals. FFR was employed because it provides an objective and physiological measure of neural activity that can reflect formant encoding. A mathematical model was used to describe vowel confusion patterns based on the neural responses to vowel formant cues. The major findings were (1) there were large variations in the accuracy of vowel formant encoding across listeners as indexed by the FFR, (2) these variations were systematically related to vowel recognition performance, and (3) the mathematical model of vowel identification was successful in predicting good vs poor vowel identification performers based exclusively on physiological data.

Talker Versus Dialect Effects on Speech Intelligibility: A Symmetrical Study

This study investigates the relative effects of talker-specific variation and dialect-based variation on speech intelligibility. Listeners from two dialects of American English performed speech-in-noise tasks with sentences spoken by talkers of each dialect. An initial statistical model showed no significant effects for either talker or listener dialect group, and no interaction. However, a mixed-effects regression model including several acoustic measures of the talker's speech revealed a subtle effect of talker dialect once the various acoustic dimensions were accounted for. Results are discussed in relation to other recent studies of cross-dialect intelligibility.

The influence of dialect upon the perception of dysarthic speech

The purpose of this study was to determine the influence of dialect upon the perception of dysarthric speech. Speakers and listeners were self-identifying as either Caucasian American or African American. Three speakers were Caucasian American, three were African American. Four speakers had experienced a CVA and were dysarthric. Listeners were age matched and were equally divided for gender. Readers recorded 14 word sentences from the Assessment of Intelligibility of Dysarthric Speech. Listeners provided ratings of intelligibility, comprehensibility, and acceptability. Own-race biases were found for all measures; however, significant findings were found for intelligibility and comprehensibility in that the Caucasian Americans provided significantly higher scores for Caucasian American speakers. Clinical implications are discussed.