Saravanan Elangovan

Internet-based tele-audiometry system for the assessment of hearing: a pilot study.

The application of tele-audiology is in its infancy. Several systems have been developed to screen hearing, yet the application of real-time diagnostic audiology to a remote location is new. This paper describes a tele-audiometric system developed for the application of realtime diagnostic audiometry via the Internet. A pilot study evaluated 31 adult participants in a double-blind study of two different systems (i.e., conventional versus Internet-based) for assessing auditory thresholds. The threshold data show substantial agreement between the two systems. Mean thresholds varied by no more than 1.3 dB, well within established variability of audiometric testing. This pilot study demonstrated the feasibility of real-time Internet-based assessment of hearing. The system allows this remote assessment of hearing without an audiologist on site. Further investigation will assess of outcomes and costs.

Auditory temporal resolution in normal-hearing preschool children revealed by word recognition in continuous and interrupted noise.

The purpose of this study was to examine temporal resolution in normal-hearing preschool children. Word recognition was evaluated in quiet and in spectrally identical continuous and interrupted noise at signal-to-noise ratios (S/Ns) of 10, 0, and -10 dB. Sixteen children 4 to 5 years of age and eight adults participated. Performance decreased with decreasing S/N. At poorer S/Ns, participants demonstrated superior performance or a release from masking in the interrupted noise. Adults performed better than children, yet the release from masking was equivalent. Collectively these findings are consistent with the notion that preschool children suffer from poorer processing efficiency rather than temporal resolution per se.

Natural boundaries in gap detection are related to categorical perception of stop consonants.

Objectives: The hypothesis that a natural auditory psychophysical discontinuity contributes to a perceptual category boundary between voiced and voiceless English stop consonants was examined. Design: 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/. Results: 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). Conclusions: 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.

Temporal processing in low-frequency channels: effects of age and hearing loss in middle-aged listeners.

BACKGROUND Hearing loss and age interfere with the auditory systems ability to process temporal changes in the acoustic signal. A key unresolved question is whether high-frequency sensorineural hearing loss (HFSNHL) affects temporal processing in the low-frequency region where hearing loss is minimal or nonexistent. A second unresolved question is whether changes in hearing occur in middle-aged subjects in the absence of HFSNHL. PURPOSE The purpose of this study was twofold: (1) to examine the influence of HFSNHL and aging on the auditory temporal processing abilities of low-frequency auditory channels with normal hearing sensitivity and (2) to examine the relations among gap detection measures, self-assessment reports of understanding speech, and functional measures of speech perception in middle-aged individuals with and without HFSNHL. RESEARCH DESIGN The subject groups were matched for either age (middle age) or pure-tone sensitivity (with or without hearing loss) to study the effects of age and HFSNHL on behavioral and functional measures of temporal processing and word recognition performance. These effects were analyzed by individual repeated-measures analyses of variance. Post hoc analyses were performed for each significant main effect and interaction. The relationships among the measures were analyzed with Pearson correlations. STUDY SAMPLE Eleven normal-hearing young adults (YNH), eight normal-hearing middle-aged adults (MANH), and nine middle-aged adults with HFSNHL were recruited for this study. Normal hearing sensitivity was defined as pure-tone thresholds ≤25 dB HL for octave frequencies from 250 to 8000 Hz. HFSNHL was defined as pure-tone thresholds ≤25 dB HL from 250 to 2000 Hz and ≥35 dB HL from 3000 to 8000 Hz. DATA COLLECTION AND ANALYSIS Gap detection thresholds (GDTs) were measured under within-channel and between-channel conditions with the stimulus spectrum limited to regions of normal hearing sensitivity for the HFSNHL group (i.e., <2000 Hz). Self-perceived hearing problems were measured by a questionnaire (Abbreviated Profile of Hearing Aid Benefit), and word recognition performance was assessed under four conditions: quiet and babble, with and without low-pass filtering (cutoff frequency = 2000 Hz). RESULTS The effects of HFSNHL and age were found for gap detection, self-perceived hearing problems, and word recognition in noise. The presence of HFSNHL significantly increased GDTs for stimuli presented in regions of normal pure-tone sensitivity. In addition, middle-aged subjects with normal hearing sensitivity reported significantly more problems hearing in background noise than the young normal-hearing subjects. Significant relationships between self-report measures of hearing ability in background noise and word recognition in babble were found. CONCLUSIONS The conclusions from the present study are twofold: (1) HFSNHL may have an off-channel impact on auditory temporal processing, and (2) presenescent changes in the auditory system of MANH subjects increased self-perceived problems hearing in background noise and decreased functional performance in background noise compared with YNH subjects.

A Comparison of the mismatch negativity and a differential waveform response

A mismatch negativity response (MMN) and a new differential waveform were derived in an effort to evaluate a neural refractory or recovery effect in adult listeners. The MMN was elicited using oddball test runs in which the standard and deviant stimuli differed in frequency. To derive the differential waveform, the same standard and deviant stimuli were presented alone. MMN responses were obtained by subtracting the averaged responses to standards from the deviants. The differential waveforms were obtained by subtracting the averaged responses to standards presented alone from deviants presented alone. Scalp topography for the MMN and differential waveforms were similar. A significant (p<.05) positive and negative correlation was found between the earlier and later components of the bimodal MMN and the N1 and P2 component of the differential waveform, respectively. Further, N1 and P2 of the differential waveform were significant (p<.05) predictor variables of early and late peak amplitudes of the MMN. These results suggest that refractory effects may overlay/modify the morphology of the MMN waveform. Sumario Se obtuvo una respuesta de negatividad desigual (MMN) y una nueva onda “diferencial” en un esfuerzo por evaluar un efecto neural refractario o de recuperación en sujetos adultos. La MMN fue generada utilizando cursos peculiares de prueba en los que el estimulo estándar y el alterado tenían frecuencias diferentes. Para derivar la onda diferencial, se presentaron el mismo estímulo estándar y el alterado en forma aislada. Las respuestas MMN se obtuvieron restando las respuestas promediadas estándar de las alteradas. Las formas de onda diferenciales se obtuvieron restando las respuestas promediadas a estímulos estándar presentados aisladamente, de los estímulos alterados presentados también en forma aislada. La topografía craneana de los MMN y las onda diferenciales fueron similares. Se encontraron correlaciones positivas y negativas significativas (p<.05) entre los componentes tempranos y tardíos de la MMN bi-modal y de los componentes N1 y P2 de la onda diferencial, respectivamente. Más aún, los componentes N1 y P2 de la onda diferencial fueron variables de predicción significativas (p<.05) de los picos tempranos y tardíos de amplitud de las MMN. Estos resultados sugieren que los efectos refractarios pueden cubrir/modificar la morfología de las onda de la MMN.

Interactive effects of high-pass filtering and masking noise on word recognition.

Objectives: This study sought to examine the word recognition performance in noise of individuals with a simulated low-frequency hearing loss. The goal was to understand how low-frequency hearing impairment affects performance on tasks that challenge temporal processing skills. Methods: Twenty-two normal-hearing young adults participated. Monosyllabic words were presented in continuous and interrupted noise at 3 signal-to-noise ratios of −10, 0, and +10 dB. High-pass filtering of the stimuli at 3 different cutoff frequencies (ie, 1,000, 1,250, and 1,500 Hz) simulated the low-frequency hearing impairment. Results: In general, performance decreased with increasing cutoff frequency, was higher for more favorable signal-to-noise ratios, and was superior in the interrupted condition relative to the continuous noise condition. One important revelation was that the magnitude of the performance superiority observed in the interrupted noise condition did not diminish with high-pass filtering; ie, the release from masking in interrupted noise was preserved. Conclusions: The results of the present study complement previous findings in which this paradigm was used with low-pass filtering to simulate a high-frequency hearing loss. That is to say, low-frequency hearing channels are inherently poorer than high-frequency channels in temporal resolution.