Objectives: Recent studies in animals indicate that even moderate levels of exposure to noise can damage synaptic ribbons between the inner hair cells and auditory nerve fibers without affecting audiometric thresholds, giving rise to the use of the term “hidden hearing loss” (HHL). Despite evidence across several animal species, there is little consistent evidence for HHL in humans. The aim of the study is to evaluate potential electrophysiological changes specific to individuals at risk for HHL. Design: Participants forming the high-risk experimental group consisted of 28 young normal-hearing adults who participated in marching band for at least 5 years. Twenty-eight age-matched normal-hearing adults who were not part of the marching band and had little or no history of recreational or occupational exposure to loud sounds formed the low-risk control group. Measurements included pure tone audiometry of conventional and high frequencies, distortion product otoacoustic emissions, and electrophysiological measures of auditory nerve and brainstem function as reflected in the click-evoked auditory brainstem response (ABR). In experiment 1, ABRs were recorded in a quiet background across stimulus levels (30–90 dB nHL) presented in 10 dB steps. In experiment 2, the ABR was elicited by a 70 dB nHL click stimulus presented in a quiet background, and in the presence of simultaneous ipsilateral continuous broadband noise presented at 50, 60, and 70 dB SPL using an insert earphone (Etymotic, ER2). Results: There were no differences between the low- and high-risk groups in audiometric thresholds or distortion product otoacoustic emission amplitude. Experiment 1 demonstrated smaller wave-I amplitudes at moderate and high sound levels for high-risk compared to low-risk group with similar wave III and wave V amplitude. Enhanced amplitude ratio V/I, particularly at moderate sound level (60 dB nHL), suggesting central compensation for reduced input from the periphery for high-risk group. The results of experiment 2 show that the decrease in wave I amplitude with increasing background noise level was relatively smaller for the high-risk compared to the low-risk group. However, wave V amplitude reduction was essentially similar for both groups. These results suggest that masking induced wave I amplitude reduction is smaller in individuals at high risk for cochlear synaptopathy. Unlike previous studies, we did not observe a difference in the noise-induced wave V latency shift between low- and high-risk groups. Conclusions: Results of experiment 1 are consistent with findings in both animal studies (that suggest cochlear synaptopathy involving selective damage of low-spontaneous rate and medium-spontaneous rate fibers), and in several human studies that show changes in a range of ABR metrics that suggest the presence of cochlear synaptopathy. However, without postmortem examination by harvesting human temporal bone (the gold standard for identifying synaptopathy) with different noise exposure background, no direct inferences can be derived for the presence/extent of cochlear synaptopathy in high-risk group with high sound over-exposure history. Results of experiment 2 demonstrate that to the extent response amplitude reflects both the number of neural elements responding and the neural synchrony of the responding elements, the relatively smaller change in response amplitude for the high-risk group would suggest a reduced susceptibility to masking. One plausible mechanism would be that suppressive effects that kick in at moderate to high levels are different in these two groups, particularly at moderate levels of the masking noise. Altogether, a larger scale dataset with different noise exposure background, longitudinal measurements (changes due to recreational over-exposure by studying middle-school to high-school students enrolled in marching band) with an array of behavioral and electrophysiological tests are needed to understand the complex pathogenesis of sound over-exposure damage in normal-hearing individuals.

This study aimed to determine (a) the influence of noise exposure background (NEB) on the peripheral and central auditory system functioning and (b) the influence of NEB on speech recognition in noise abilities in student musicians. Twenty non-musician students with self-reported low NEB and 18 student musicians with self-reported high NEB completed a battery of tests that consisted of physiological measures, including auditory brainstem responses (ABRs) at three different stimulus rates (11.3 Hz, 51.3 Hz, and 81.3 Hz), and P300, and behavioral measures including conventional and extended high-frequency audiometry, consonant–vowel nucleus–consonant (CNC) word test and AzBio sentence test for assessing speech perception in noise abilities at −9, −6, −3, 0, and +3 dB signal to noise ratios (SNRs). The NEB was negatively associated with performance on the CNC test at all five SNRs. A negative association was found between NEB and performance on the AzBio test at 0 dB SNR. No effect of NEB was found on the amplitude and latency of P300 and the ABR wave I amplitude. More investigations of larger datasets with different NEB and longitudinal measurements are needed to investigate the influence of NEB on word recognition in noise and to understand the specific cognitive processes contributing to the impact of NEB on word recognition in noise.

Audacity is a multi-platform free, open-source audio recorder and editor software. The advantage of Audacity software is as follows: easy installation and simple visual interface, no registrations or hardware requirements, and availability at no cost might make it a preferred software to carry out class demonstrations and lab activities for an undergraduate course in the Communication Sciences and Disorders discipline. The tutorial aims to illustrate how Audacity software can be used to demonstrate various psychoacoustic phenomena commonly taught in undergraduate Hearing Science courses. This tutorial is divided into fundamental and advanced concepts from the pedagogy and student learning standpoint. The fundamental concepts involve using sine waves to demonstrate frequency, amplitude, and phase related to auditory perception. The advanced concepts include the generation of complex periodic non-speech signals, wave superposition, beats, missing fundamental frequency, demonstration of different filters, and amplitude and frequency modulation. Future research is needed to evaluate the benefits of using Audacity software for psychoacoustical demonstrations in an undergraduate Hearing Science course.

The Auditory Steady-State Response (ASSR) provides objective and ear-specific information essential for early and appropriate intervention. Test–retest reliability is essential for audiological monitoring. The test–retest reliability of the ASSR has received limited attention. Only a handful of studies found in the literature investigated the test–retest reliability of old-generation ASSR using amplitude or mixed modulated stimuli. However, to our knowledge, no published reports have specifically examined the test–retest reliability of the next-generation ASSR using Chirp family stimuli as implemented in the Interacoustics Eclipse system. This pilot study investigated (a) the test–retest reliability of air conduction (AC) ASSR thresholds across two test sessions and (b) the relationship between differences in ASSR thresholds across two sessions to the residual noise levels in normal-hearing adults. Methods: Fifteen normal-hearing adults (12 females) (30 ears) with an average age of 28 years were recruited for the study. The ASSRs were recorded using a two-channel recording montage. The automatic default stimuli and recording protocol using 90 Hz ASSR, and the accuracy method (p < 0.01) as implemented in the Eclipse system is used to measure ASSR. Results: The study demonstrated strong test–retest reliability for ASSR across frequencies (500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz). Notably, the highest reliability was observed at 500 Hz. The mean test–retest reliability of ASSR was found to be comparable to pure-tone thresholds, but the intra-subject variability is higher for ASSR compared to pure-tone thresholds. Additionally, no significant correlation was found between the difference in ASSR residual noise levels at the threshold and the difference in ASSR thresholds at all tested frequencies. Conclusion: The next-generation system demonstrated strong test–retest reliability across the frequencies examined in this pilot study. Particularly, an improvement in reliability was observed at 500 Hz compared to the old-generation ASSR. This enhancement can be attributed to the utilization of narrow-band CE-chirp stimuli, which generate large amplitude responses, and the implementation of an improved detection paradigm involving multiple harmonics spectral and phase analysis. This pilot study only enrolled adults with normal hearing, and future investigations should include a larger sample size comprising both normal-hearing and hearing-impaired individuals, as well as the pediatric population.

Objective: Human studies enrolling individuals at high risk for cochlear synaptopathy (CS) have reported difficulties in speech perception in adverse listening conditions. The aim of this study is to determine if these individuals show a degradation in the neural encoding of speech in quiet and in the presence of background noise as reflected in neural phase-locking to both envelope periodicity and temporal fine structure (TFS). To our knowledge, there are no published reports that have specifically examined the neural encoding of both envelope periodicity and TFS of speech stimuli (in quiet and in adverse listening conditions) among a sample with loud-sound exposure history who are at risk for CS. Method: Using scalp-recorded frequency-following response (FFR), the authors evaluated the neural encoding of envelope periodicity (FFR _ENV ) and TFS (FFR _TFS ) for a steady-state vowel (English back vowel /u/) in quiet and in the presence of speech-shaped noise presented at +5- and 0 dB SNR. Participants were young individuals with normal hearing who participated in the marching band for at least 5 years (high-risk group) and non–marching band group with low-noise exposure history (low-risk group). Results: The results showed no group differences in the neural encoding of either the FFR _ENV or the first formant (F1) in the FFR _TFS in quiet and in noise. Paradoxically, the high-risk group demonstrated enhanced representation of F2 harmonics across all stimulus conditions. Conclusions: These results appear to be in line with a music experience–dependent enhancement of F2 harmonics. However, due to sound overexposure in the high-risk group, the role of homeostatic central compensation cannot be ruled out. A larger scale data set with different noise exposure background, longitudinal measurements with an array of behavioral and electrophysiological tests is needed to disentangle the nature of the complex interaction between the effects of central compensatory gain and experience-dependent enhancement.