Fast Click Rate Electrocochleography and Auditory Brainstem Response in Normal-Hearing Adults Using Continuous Loop Averaging Deconvolution

Objectives: Using the continuous loop averaging deconvolution (CLAD) technique for conventional electrocochleography (ECochG) and auditory brainstem response (ABR) recordings, the effects of testing at high stimulus rates may have the potential to diagnose disorders of the inner ear and auditory nerve. First, a body of normative data using the CLAD technique must be established. Design: Extratympanic click ECochG and ABR to seven stimulus rates using CLAD were measured simultaneously from a tympanic membrane electrode and surface electrodes on the forehead and mastoid of 42 healthy individuals. Results: Results showed that the compound action potential (AP) of the ECochG and waves I, III, and V of the ABR decreased in amplitude and increased in latency as stimulus rate was increased from standard 7.1 clicks/s up to 507.81 clicks/s, with sharp reduction in AP amplitude at 97.66 clicks/s and reaching asymptote at 292.97 clicks/s. The summating potential (SP) of the ECochG, however, stayed relatively stable, resulting in increased SP/AP ratios with increasing rate. The SP/AP amplitude ratio showed more stability than AP amplitude findings, thus it is recommended for use in evaluation of cochlear and neural response. Conclusions: Results of both amplitude and latency data from this normative neural adaptation function of the auditory pathway serves as guide for improving diagnostic utility of both ECochG and ABR using CLAD as a reliable technique in distinguishing inner ear and auditory nerve disorders.

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Characterizing Speech Intelligibility in Noise After Wide Dynamic Range Compression

Objectives: The effects of nonlinear signal processing on speech intelligibility in noise are difficult to evaluate. Often, the effects are examined by comparing speech intelligibility scores with and without processing measured at fixed signal to noise ratios (SNRs) or by comparing the adaptive measured speech reception thresholds corresponding to 50% intelligibility (SRT50) with and without processing. These outcome measures might not be optimal. Measuring at fixed SNRs can be affected by ceiling or floor effects, because the range of relevant SNRs is not know in advance. The SRT50 is less time consuming, has a fixed performance level (i.e., 50% correct), but the SRT50 could give a limited view, because we hypothesize that the effect of most nonlinear signal processing algorithms at the SRT50 cannot be generalized to other points of the psychometric function. Design: In this article, we tested the value of estimating the entire psychometric function. We studied the effect of wide dynamic range compression (WDRC) on speech intelligibility in stationary, and interrupted speech-shaped noise in normal-hearing subjects, using a fast method-based local linear fitting approach and by two adaptive procedures. Results: The measured performance differences for conditions with and without WDRC for the psychometric functions in stationary noise and interrupted speech-shaped noise show that the effects of WDRC on speech intelligibility are SNR dependent. Conclusions: We conclude that favorable and unfavorable effects of WDRC on speech intelligibility can be missed if the results are presented in terms of SRT50 values only.

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Evaluating the Precision of Auditory Sensory Memory as an Index of Intrusion in Tinnitus

Objectives: The purpose of this study was to investigate the potential of measures of auditory short-term memory (ASTM) to provide a clinical measure of intrusion in tinnitus. Design: Response functions for six normal listeners on a delayed pitch discrimination task were contrasted in three conditions designed to manipulate attention in the presence and absence of simulated tinnitus: (1) no-tinnitus, (2) ignore-tinnitus, and (3) attend-tinnitus. Results: Delayed pitch discrimination functions were more variable in the presence of simulated tinnitus when listeners were asked to divide attention between the primary task and the amplitude of the tinnitus tone. Conclusions: Changes in the variability of auditory short-term memory may provide a novel means of quantifying the level of intrusion associated with the tinnitus percept during listening.

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Comparison of Different Electrode Configurations for the oVEMP With Bone-Conducted Vibration

Objectives: This study was performed to compare three electrode configurations for the ocular vestibular evoked myogenic potentials (oVEMPs)—“standard,” “sternum,” and “nose”—by making use of bone-conducted stimuli (at the level of Fz with a minishaker). In the second part, we compared the test–retest reliability of the standard and nose electrode configuration on the oVEMP parameters. Design: This study had a prospective design. Fourteen healthy subjects participated in the first part (4 males, 10 females; average age = 23.4 (SD = 2.6) years; age range 19.9 to 28.3 years) and second part (3 males, 11 females; average age = 22.7 (SD = 2.4) years; age range 20.0 to 28.0 years) of the study. OVEMPs were recorded making use of a hand-held bone conduction vibrator (minishaker). Tone bursts of 500 Hz (rise/fall time = 2 msec; plateau time = 2 msec; repetition rate = 5.1 Hz) were applied at a constant stimulus intensity level of 140 dB FL. Results: PART 1: The n10–p15 amplitude obtained with the standard electrode configuration (mean = 15.8 μV; SD = 6.3 μV) was significantly smaller than the amplitude measured with the nose (Z = −3.3; p = 0.001; mean = 35.0 μV; SD = 19.1 μV) and sternum (Z = −3.3; p = 0.001; mean = 27.1 μV; SD = 12.2 μV) electrode configuration. The p15 latency obtained with the nose electrode configuration (mean = 14.2 msec; SD = 0.54 msec) was significantly shorter than the p15 latency measured with the standard (Z = −3.08; p = 0.002) (mean = 14.9 msec; SD = 0.75 msec) and sternum (Z = −2.98; p = 0.003; mean = 15.4 msec; SD = 1.07 msec) electrode configuration. There were no differences between the n10 latencies of the three electrode configurations. The 95% prediction intervals (given by the mean ± 1.96 * SD) for the different interocular ratio values were [−41.2; 41.2], [−37.2; 37.2], and [−25.9; 25.9] for standard, sternum, and nose electrode configurations, respectively. PART 2: Intraclass correlation (ICC) values calculated for the oVEMP parameters obtained with the standard electrode configuration showed fair to good reliability for the parameters n10–p15 amplitude (ICC = 0.51), n10 (ICC = 0.52), and p15 (ICC = 0.60) latencies. The ICC values obtained for the parameters acquired with the nose electrode configuration demonstrated a poor reliability for the n10 latency (ICC = 0.37), a fair to good reliability for the p15 latency (ICC = 0.47) and an excellent reliability for the n10–p15 amplitude (ICC = 0.85). Conclusions: This study showed the possible benefits from alternative electrode configurations for measuring bone-conducted-evoked oVEMPs in comparison with the standard electrode configuration. The nose configuration seems promising, but further research is required to justify clinical use of this placement.

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Effects of Long-Term Musical Training on Cortical Auditory Evoked Potentials

Objective: Evidence suggests that musicians, as a group, have superior frequency resolution abilities when compared with nonmusicians. It is possible to assess auditory discrimination using either behavioral or electrophysiologic methods. The purpose of this study was to determine if the acoustic change complex (ACC) is sensitive enough to reflect the differences in spectral processing exhibited by musicians and nonmusicians. Design: Twenty individuals (10 musicians and 10 nonmusicians) participated in this study. Pitch and spectral ripple discrimination were assessed using both behavioral and electrophysiologic methods. Behavioral measures were obtained using a standard three interval, forced choice procedure. The ACC was recorded and used as an objective (i.e., nonbehavioral) measure of discrimination between two auditory signals. The same stimuli were used for both psychophysical and electrophysiologic testing. Results: As a group, musicians were able to detect smaller changes in pitch than nonmusician. They also were able to detect a shift in the position of the peaks and valleys in a ripple noise stimulus at higher ripple densities than non-musicians. ACC responses recorded from musicians were larger than those recorded from non-musicians when the amplitude of the ACC response was normalized to the amplitude of the onset response in each stimulus pair. Visual detection thresholds derived from the evoked potential data were better for musicians than non-musicians regardless of whether the task was discrimination of musical pitch or detection of a change in the frequency spectrum of the ripple noise stimuli. Behavioral measures of discrimination were generally more sensitive than the electrophysiologic measures; however, the two metrics were correlated. Conclusions: Perhaps as a result of extensive training, musicians are better able to discriminate spectrally complex acoustic signals than nonmusicians. Those differences are evident not only in perceptual/behavioral tests but also in electrophysiologic measures of neural response at the level of the auditory cortex. While these results are based on observations made from normal-hearing listeners, they suggest that the ACC may provide a non-behavioral method of assessing auditory discrimination and as a result might prove useful in future studies that explore the efficacy of participation in a musically based, auditory training program perhaps geared toward pediatric or hearing-impaired listeners.

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Spectral Ripple Discrimination in Normal-Hearing Infants

Objectives: Spectral resolution is a correlate of open-set speech understanding in postlingually deaf adults and prelingually deaf children who use cochlear implants (CIs). To apply measures of spectral resolution to assess device efficacy in younger CI users, it is necessary to understand how spectral resolution develops in normal-hearing children. In this study, spectral ripple discrimination (SRD) was used to measure listeners’ sensitivity to a shift in phase of the spectral envelope of a broadband noise. Both resolution of peak to peak location (frequency resolution) and peak to trough intensity (across-channel intensity resolution) are required for SRD. Design: SRD was measured as the highest ripple density (in ripples per octave) for which a listener could discriminate a 90° shift in phase of the sinusoidally-modulated amplitude spectrum. A 2 × 3 between-subjects design was used to assess the effects of age (7-month-old infants versus adults) and ripple peak/trough “depth” (10, 13, and 20 dB) on SRD in normal-hearing listeners (experiment 1). In experiment 2, SRD thresholds in the same age groups were compared using a task in which ripple starting phases were randomized across trials to obscure within-channel intensity cues. In experiment 3, the randomized starting phase method was used to measure SRD as a function of age (3-month-old infants, 7-month-old infants, and young adults) and ripple depth (10 and 20 dB in repeated measures design). Results: In experiment 1, there was a significant interaction between age and ripple depth. The infant SRDs were significantly poorer than the adult SRDs at 10 and 13 dB ripple depths but adult-like at 20 dB depth. This result is consistent with immature across-channel intensity resolution. In contrast, the trajectory of SRD as a function of depth was steeper for infants than adults suggesting that frequency resolution was better in infants than adults. However, in experiment 2 infant performance was significantly poorer than adults at 20 dB depth suggesting that variability of infants’ use of within-channel intensity cues, rather than better frequency resolution, explained the results of experiment 1. In experiment 3, age effects were seen with both groups of infants showing poorer SRD than adults but, unlike experiment 1, no significant interaction between age and depth was seen. Conclusions: Measurement of SRD thresholds in individual 3 to 7-month-old infants is feasible. Performance of normal-hearing infants on SRD may be limited by across-channel intensity resolution despite mature frequency resolution. These findings have significant implications for design and stimulus choice for applying SRD for testing infants with CIs. The high degree of variability in infant SRD can be somewhat reduced by obscuring within-channel cues.

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Smartphone-Based Hearing Screening at Primary Health Care Clinics

Objective: To evaluate the performance of smartphone-based hearing screening with the hearScreen™ application in terms of sensitivity, specificity, referral rates, and time efficiency at two primary health care clinics. Design: Nonprobability purposive sampling was used at both clinics. A total of 1236 participants (mean age: 37.8 ± SD 17.9 and range 3 to 97 years; 71.3% female) were included in the final analysis. Participants were screened using the hearScreen™ application following a two-step screening protocol and diagnostic pure-tone audiometry to confirm hearing status. Results: Sensitivity and specificity for smartphone screening was 81.7 and 83.1%, respectively, with a positive and negative predictive value of 87.6 and 75.6%, respectively. Sex [χ2(1, N = 126) = 0.304, p > 0.05] and race [χ2(1, N = 126) = 0.169, p > 0.05)] had no significant effect on screening outcome for children while for adults age (p

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