Vijaya Kumar Narne

Assessing spectral and temporal processing in children and adults using temporal modulation transfer function (TMTF), Iterated Ripple Noise (IRN) perception, and spectral ripple discrimination (SRD).

BACKGROUND There are many clinically available tests for the assessment of auditory processing skills in children and adults. However, there is limited data available on the maturational effects on the performance on these tests. PURPOSE The current study investigated maturational effects on auditory processing abilities using three psychophysical measures: temporal modulation transfer function (TMTF), iterated ripple noise (IRN) perception, and spectral ripple discrimination (SRD). RESEARCH DESIGN A cross-sectional study. Three groups of subjects were tested: 10 adults (18-30 yr), 10 older children (12-18 yr), and 10 young children (8-11 yr) DATA COLLECTION AND ANALYSIS Temporal envelope processing was measured by obtaining thresholds for amplitude modulation detection as a function of modulation frequency (TMTF; 4, 8, 16, 32, 64, and 128 Hz). Temporal fine structure processing was measured using IRN, and spectral processing was measured using SRD. RESULTS The results showed that young children had significantly higher modulation thresholds at 4 Hz (TMTF) compared to the other two groups and poorer SRD scores compared to adults. The results on IRN did not differ across groups. CONCLUSIONS The results suggest that different aspects of auditory processing mature at different age periods and these maturational effects need to be considered while assessing auditory processing in children.

Audiological profiling of 198 individuals with auditory neuropathy spectrum disorder

Abstract Objective: The study aimed at exploring the audiological characteristics and the relationship between speech identification scores with cortical evoked potential measures and hearing aid benefit in individuals with auditory neuropathy spectrum disorder (ANSD). Study design: We initiated a retrospective study of patients who were diagnosed as having ANSD. In 198 patients with ANSD, patient history, risk factors, degree and configuration of hearing loss, speech identification scores in quiet and noise, otoacoustic emissions (OAE), immittance evaluation, auditory brainstem responses (ABR), long latency responses (LLR) and hearing aid benefit were assessed. Results: The results showed that the majority of the patients had bilateral ANSD with a female to male ratio of 1.25:1 with the majority having a rising configuration of hearing loss. OAEs were present in most with absent stapedial reflexes and ABR. The study also showed that individuals with ANSD do obtain benefit from hearing aids and it is related to the presence of LLR. Conclusions: The present study emphasizes the audiological characteristics of a large group with ANSD. Among the management options, hearing aids were found to be useful in only a few of the patients and other rehabilitation options, such as cochlear implants, need to be explored in future studies. Currently, the determining factors for benefit with hearing aid are speech identification scores and cortical auditory evoked potentials.

Perception of speech with envelope enhancement in individuals with auditory neuropathy and simulated loss of temporal modulation processing

Individuals with auditory neuropathy (AN) often suffer from temporal processing deficits causing speech perception difficulties. In the present study an envelope enhancement scheme that incorporated envelope expansion was used to reduce the effects of temporal deficits. The study involved two experiments. In the first experiment, to simulate the effects of reduced temporal resolution, temporally smeared speech stimuli were presented to listeners with normal hearing. The results revealed that temporal smearing of the speech signal reduced identification scores. With the envelope enhancement of the speech signal prior to being temporally smeared, identification scores improved significantly compared to temporally smeared condition. The second experiment assessed speech perception in twelve individuals with AN, using unprocessed and envelope-enhanced speech signals. The results revealed improvement in speech identification scores for the majority of individuals with AN when the envelope of the speech signal was enhanced. However, envelope enhancement was not able to improve speech identification scores for individuals with AN who had very poor unprocessed speech scores. Overall, the results of the present study suggest that applying envelope enhancement strategies in hearing aids might provide some benefits to many individuals with AN.

Time–frequency analysis of transient evoked-otoacoustic emissions in individuals with auditory neuropathy spectrum disorder

The aim of the study was to describe and quantify the cochlear active mechanisms in individuals with Auditory Neuropathy Spectrum Disorders (ANSD). Transient Evoked Otoacoustic Emissions (TEOAEs) were recorded in 15 individuals with ANSD and 22 individuals with normal hearing. TEOAEs were analyzed by Wavelet transform method to describe and quantify the characteristics of TEOAEs in narrow-band frequency regions. It was noted that the amplitude of TEOAEs was higher and latency slightly shorter in individuals with ANSD compared to normal hearing individuals at low and mid frequencies. The increased amplitude and reduced latencies of TEOAEs in ANSD group could be attributed to the efferent system damage, especially at low and mid frequencies seen in individuals with ANSD. Thus, wavelet analysis of TEOAEs proves to be another important tool to understand the patho-physiology in individuals with ANSD.

Effect of companding on speech recognition in quiet and noise for listeners with ANSD

Abstract Objective: The present study assesses the effect of companding on speech perception in quiet and noise for listeners with auditory neuropathy spectrum disorder (ANSD). Design: Speech perception was assessed using speech reception threshold in noise (SRTn) for sentences and consonant identification in quiet and at different signal-to-noise ratios (15, 10, 5, and 0 dB SNR). Study sample: Ten ANSD listeners and normal-hearing listeners participated in the study. Results: ANSD listeners required significantly higher SRTn when compared to the normal-hearing listeners. Companding reduced SRTn more significantly in listeners with ANSD, but for normal-hearing listeners there was only a marginal reduction. In the consonant identification task, ANSD listeners performed poorer than normal-hearing listeners in quiet and noise. Companding improved consonant identification in quiet and at 15 dB SNR for listeners with ANSD, whereas no improvement was observed in normal-hearing listeners. Conclusion: Results of the present study demonstrate that companding improved speech perception in quiet and noise for ANSD listeners. The amount of improvement is higher at higher SNRs. In normal-hearing listeners, companding showed marginal improvement in both quiet and noise. The findings are discussed for rehabilitation of ANSD listeners by hearing aids which incorporate the companding strategy.

Long Ringing Cochlear Microphonics - Not Unique to Auditory Neuropathy Spectrum Disorder in Children

Long Ringing Cochlear Microphonics - Not Unique to Auditory Neuropathy Spectrum Disorder in Children Background: The detection of cochlear microphonics in surface recordings has been considered a distinctive sign of outer hair cell integrity in participants with auditory neuropathy spectrum disorder. The study highlights that this notion could result in misdiagnosis of patients. Methods: The study reports three children with sloping hearing loss who were misdiagnosed as auditory neuropathy spectrum disorder based on absence of auditory brainstem response and presence of long ringing cochlear microphonics. The study also reports of three children with abnormal cochlear microphonics who have neurological abnormalities. Results: The abnormal cochlear microphonics (long ringing) with absent auditory brainstem response was noted in sloping hearing loss participants. In addition, abnormal cochlear microphonics was also observed along with auditory brainstem response in children with neurological abnormalities. Conclusion: Our results show that abnormal CM detection in surface recording is not a distinctive feature of auditory neuropathy spectrum disorder and participants who are diagnosed with auditory neuropathy spectrum disorder based on traditional diagnostic criteria should be reviewed to rule out possible misdiagnosis.

Development of equally intelligible Telugu sentence-lists to test speech recognition in noise

Abstract Objective: To develop sentence lists in the Telugu language for the assessment of speech recognition threshold (SRT) in the presence of background noise through identification of the mean signal-to-noise ratio required to attain a 50% sentence recognition score (SRTn). Design: This study was conducted in three phases. The first phase involved the selection and recording of Telugu sentences. In the second phase, 20 lists, each consisting of 10 sentences with equal intelligibility, were formulated using a numerical optimisation procedure. In the third phase, the SRTn of the developed lists was estimated using adaptive procedures on individuals with normal hearing. Study sample: A total of 68 native Telugu speakers with normal hearing participated in the study. Of these, 18 (including the speakers) performed on various subjective measures in first phase, 20 performed on sentence/word recognition in noise for second phase and 30 participated in the list equivalency procedures in third phase. Results: In all, 15 lists of comparable difficulty were formulated as test material. The mean SRTn across these lists corresponded to −2.74 (SD = 0.21). Conclusions: The developed sentence lists provided a valid and reliable tool to measure SRTn in Telugu native speakers.

The Developement of Hindi Sentence Test for Speech Recognition in Noise

Background : The aim of the study was to develop a test material in Hindi language for assessing sentence recognition threshold in noise. Material and Methods : The study was conducted in two phases. First phase involved three experiments. First experiment consisted of the collection and recording of the sentence material. In the second experiment, sentence perception was assessed at five signal to noise ratios to check for the equalization of sentence material in terms of intelligibilty. This was done on 25 native speakers of Hindi language with normal hearing sensitivity. In the final experiment, 20 different lists with 10 sentences in each were formulated. The second phase of the experiment involved estimation of signal to noise ratio required to obtain 50% correct sentence identification score (SNR 50) and the test reliability of the lists was assessed. The estimation of SNR 50 was done on 30 native speakers of Hindi language with normal hearing sensitivity. Results : Twenty optimized lists were formulated. Lists were found to be of almost equal difficulty and to have good test reliability in normal-hearing listeners. The average SNR50 was -4.56 dB with a standard deviation of 0.45 dB. Conclusions : The developed test provides a reliable means of measuring sentence recognition threshold in noise for native speakers of Hindi.

Involvement of the Efferent Auditory System for Improvement in Speech Perception in Noise

To investigate the involvement of auditory efferents in hearing-in-noise in humans, Median olivocochlear (MOC) efferent’s functioning and speech recognition-in-noise abilities were compared in 19 subjects. MOC efferent’s function was assessed in terms of contralateral attenuation of transient evoked otoacoustic emissions (TEOAE): i.e., the reduction in TEOAE amplitude elicited by a 40, 50 and 60-dB SPL contralateral speech spectrum shaped noise. Correspondingly, the speech reception thresholds for sentences embedded in 50-dB SPL speech spectrum shaped noise (SRTn) were measured in the same ear as the TEOAEs, successively in the presence and in the absence of uncorrelated noise in the opposite ear at three different levels (i.e 40, 50, & 60 dB SPL). The results indicated there was no significant statistical correlation between the contralateral attenuation of TEOAEs and SRTn for uncorrelated noise. In addition, there was no change in SRTn for uncorrelated noise at different levels. These results were discussed in line with previous studies.

Low frequency bi-syllabic wordlists in a South-Indian language, Kannada: development, standardization and validation

Abstract Objective: The present study aimed to develop, standardize and validate low frequency bi-syllabic wordlists in Kannada, a South-Indian language. Study design: The study was conducted in three different phases. The Kannada low frequency wordlists were developed in Phase I. The procedure involved collecting bi-syllabic familiar words, recording them, selecting the words dominant in low frequency energy by acoustical (Fast Fourier) transform and statistical means (k-means clustering) then generating equivalent wordlists using psychometric function. In Phase II, all the wordlists developed were standardized through estimation of speech identification scores in 100 individuals with normal hearing and through re-verification of equivalence of wordlists’ difficulty level by obtaining psychometric function. Finally, during Phase III, lists developed were evaluated for usefulness by administering them along with conventional phonemically-balanced Kannada wordlist on 10 individuals with cochlear hearing loss having rising audiometric configurations (i.e. more loss at lower frequencies). Results: Phase I resulted in development of seven psychometrically equivalent wordlists. Speech identification scores on 100 individuals with normal hearing showed mean scores greater than 95% for all the lists at 40 dB SL. No statistical difference was noted across wordlists. Further, individuals with rising cochlear hearing loss (RCHL) performed significantly poorer when compared to normal hearing counterparts across wordlists except low frequency wordlist 4 and phonemically balanced wordlist. Conclusions: The study utilized a unique procedure for the development of wordlists which can serve as guidelines for further research. The study has resulted in standardization (along with generation of normative data) and successful validation of the lists (except list 4) developed on a clinical population, i.e. individuals with RCHL. Given the lack of availability and the current clinical/research need of such test materials, the wordlists generated from this study can be useful.