Andrew Stuart

Background During audiologic evaluations, an examination of interaural asymmetry is commonly evaluated. To date, however, interaural differences for tympanometric indices have not been reported for adults. Without documented tympanometric right-left differences, one cannot determine if asymmetries are normal or are indicative of significant clinical asymmetries. Purpose The purpose of this study was to investigate interaural asymmetries in peak compensated static acoustic admittance (Y_tm), equivalent ear canal volume (V_ea), tympanometric peak pressure (TPP), and tympanometric width (TW) in normal adults. Research Design Descriptive, correlational, and inferential measures designs were employed. Study Sample Participants were 188 otologically normal Caucasian young adults (i.e., 77 females and 111 males; M = 23.0 years, standard deviation [SD] = 2.7, range = 18‐30 years). Data Collection and Analyses Y_tm, V_ea, TPP, and TW measures were obtained bilaterally from an admittance tympanogram using a 226 Hz probe tone. Separate two-factor mixed measures analysis of variance examined the effect of ear and sex for each tympanometric index. Correlation analyses examined the association between right and left ear indices. Interaural differences in tympanometric indices were examined with independent t-tests. Critical differences, for deciding if two tympanometric indices are different between ears, were computed from the standard deviations of the right‐left ear difference for statistical confidence levels of 85, 90, 95, and 99%. Results The effect of ear was not statistically significant (p > 0.05) on any tympanometric index. Females had significantly lower Y_tm and smaller V_ea measures than males (p < 0.05). Correlations between all right and left tympanometric indices were positive and statistically significant (p < 0.05). There were no statistically significant differences in interaural differences for any of the tympanometric indices as a function of sex (p > 0.05). Critical differences, for confidence levels for 85% to 99% confidence ranged from ± 0.20‐0.36 mmhos for Y_tm, ± 0.23‐0.41 cm³ for V_ea, ± 11.1‐19.8 daPa for TPP, and ± 27.2‐48.7 daPa for TW. Conclusion A clinician can use these critical differences to determine if tympanometric index interaural differences in ears of young normal Caucasian adults are statistically significant.

The effect of age on release from masking (RFM) was examined using cortical auditory evoked potentials (CAEPs). Two speech-in-noise paradigms [i.e., fixed speech with varying signal-to-noise ratios (SNRs) and fixed noise with varying speech levels], similar to those used in behavioral measures of RFM, were employed with competing continuous and interrupted noises. Young and older normal-hearing adults participated (N = 36). Cortical responses were evoked in the fixed speech paradigm at SNRs of −10, 0, and 10 dB. In the fixed noise paradigm, the CAEP SNR threshold was determined in both noises as the lowest SNR that yielded a measurable response. RFM was demonstrated in the fixed speech paradigm with a significant amount of missing responses, longer P1 and N1 latencies, and smaller N1 response amplitudes in continuous noise at the poorest −10 dB SNR. In the fixed noise paradigm, RFM was demonstrated with significantly lower CAEP SNR thresholds in interrupted noise. Older participants demonstrated significantly longer P2 latencies and reduced P1 and N1 amplitudes. There was no evidence of a group difference in RFM in either paradigm.

Background Although numerous studies have examined regional and racial-ethnic labeling of talker identity, few have evaluated speech perception skills of listeners from the southern United States. Purpose The objective of the study was to examine the effect of competition, signal-to-noise ratio (SNR), race, and sex on sentence recognition performance in talkers from the Southern American English dialect region. Research Design A four-factor mixed-measures design was used. Study Sample Forty-eight normal-hearing young African American and White adults participated. Data Collection and Analyses The Perceptually Robust English Sentence Test Open-set was used in quiet and in continuous and interrupted noise and multitalker babble at SNRs of -10, -5, 0, and 5 dB. Results Significant main effects of competition (p < 0.001) and SNR (p < 0.001) and a competition by SNR interaction were found (p < 0.001). Performance improved with increasing SNRs. Performance was also greater in the interrupted broadband noise at poorer SNRs, relative to the other competitors. Multitalker babble performance was significantly poorer than the continuous noise at the poorer SNRs. There was no effect of race or sex on performance in quiet or competition. Conclusions Although African American English and White American English talkers living in the same geographic region demonstrate differences in speech production, their speech perception in noise does not appear to differ under the conditions examined in this study.

To explore the hypothesis that a low-frequency hearing loss would not significantly impair an individual’s auditory temporal resolution performance.

Objective: The purpose of this study was to examine the effect of three bone vibrator coupling methods on the neonate auditory brainstem response (ABR). Design: A repeated measures design was employed. Three coupling techniques were utilised (i.e. hand-held, hand-held applied force gauge and elastic band). ABRs were evoked with a bone-conducted 30 dB nHL 4000 Hz CE-Chirp octave band stimulus. A temporal bone area supero-posterior auricular position for bone vibrator placement was utilised. Study Sample: Twenty-six healthy full-term neonates participated. Results: Replicated ABRs were recorded from all neonates for each coupling method. There was a statistically significant effect of coupling on wave V latency (p < 0.001) and amplitude (p < 0.001). There was no statistical difference between the elastic band and the hand-held force gauge coupling for wave V latency and amplitude (p > 0.05). However, the hand-held coupling method produced significantly longer wave V latency and smaller amplitude versus the elastic band and hand-held force gauge (p < 0.001). Conclusions: Bone vibrator coupling method affects the neonate ABR. Clinicians should be consistent with the choice of coupling while delivering controlled bone-conducted stimuli in ABR assessments in neonates and infants.

Purpose: The purpose of the study was to examine the effect of short-term noise exposure on audiometric thresholds, distortion product otoacoustic emissions (DPOAEs), and electrocochleography (ECochG) as a function of ear and sex. Method: Preexposure and postexposure measures of audiometric thresholds, DPOAEs, and ECochG indices were examined. Sixteen male and 16 female adults participated. Participants were exposed to a 2000-Hz narrowband noise presented at 105 dBA for 10 min. Results: Following noise exposure, significantly ( p < .0001) larger auditory threshold differences were observed for left ears. Larger auditory threshold differences were also observed for 3000 and 4000 Hz versus 2000 and 6000 Hz. DPOAE absolute amplitude differences increased with decreasing L ₁ , L ₂ level ( p < .0001). DPOAE absolute amplitude differences also significantly rose with increasing f ₂ frequencies ( p < .0001). Females generally had larger DPOAE absolute amplitude differences than males ( p < .05). Summating potential amplitudes were significantly larger for female left ears following noise exposure ( p = .03). Left-ear summating potential/action potential amplitude ratios and summating potential/action potential area ratios were increased following noise exposure ( p < .05). Conclusions: Utilizing a test battery to examine the effects of short-term noise exposure can reveal the functional status of different structures in the cochlea. There appears to be a susceptibility of the left ear to short-term loud noise exposure. Findings with respect to a sex susceptibility to short-term loud noise exposure were not strong, as sex differences were only observed for a subset of the conditions.