Seminars in Hearing Research

Date: Thursday, April 24, 2025

Location: Nelson 1215

Time: Noon - 1:00 pm

Speaker: Meredith Christine Ziliak, PhD Candidate, BIO 

Title: Intensity-Dependent Effects of Small Arms Fire-Like Noise on Temporal Processing

Abstract:  Small arms fire-like (SAF) noise is characterized by a sudden onset of acute, high intensity pulses. Exposure to SAF noise is often found in military, law enforcement, and recreational occupations, leading to increased prevalence of SAF noise-induced hearing loss among participating populations. Therefore, it is important to understand how the auditory system is affected by SAF noise exposure to better inform clinical diagnostic and treatment strategies. Current studies have shown SAF noise exposure results in worsened distortion product otoacoustic emissions (DPOAEs), cochlear synaptopathy, elevated thresholds, and decreased auditory brainstem response (ABR) wave I amplitude (Altschuler et al., 2019; Lafoon et al., 2019; Malowski et al., 2022). However, as the exact condition of each noise exposure is inherently unique, it is imperative to identify how common variations affect the progression of maladaptive responses within the peripheral and central auditory systems. Several studies demonstrate intensity and sound pressure level of an auditory stressor can differentially affect the development of auditory pathologies, particularly at levels mild enough to cause temporary threshold shifts and hidden hearing loss (Gratias et al., 2021; Fernandez et al, 2015; Morgan et al., 2019). Therefore, the purpose of this study is to assess the progression of intensity-dependent SAF noise-induced changes on cochlear and subcortical auditory system function. We hypothesize that higher SAF noise exposure intensity levels will result in impaired function of high frequency afferent fibers leading to altered temporal processing indicated by responses to ABR wave morphology and complex stimuli. Higher intensity exposure levels are also hypothesized to demonstrate a delayed onset and prolonged duration of central damage compared to lower intensity levels. To test our hypotheses, we bilaterally exposed anesthetized rodent subjects to SAF noise presented at either 60, 116.5, 120, 123, or 126 dB peak sound pressure level. Electrophysiological recordings including DPOAEs, ABRs, and auditory evoked potentials to complex stimuli were recorded at baseline and post exposure days 7, 14, 28, and 56. Animals were sedated for recordings and recovered on a heating pad. Distortion product signal-to-noise ratio, click and pure tone thresholds, and power analysis of dynamic amplitude modulated stimuli and speech tokens will be assessed and discussed. This study provides a foundation for understanding how SAF noise exposure influences the development of clinically relevant hearing loss pathology. Our electrophysiological results will be supplemented with future anatomical studies to determine mechanisms underlying intensity-dependent auditory system plasticity and adaptation.

 ---

The working schedule is available here: https://purdue.edu/TPAN/hearing/shrp_schedule

The titles and abstracts of the talks will be added here: https://purdue.edu/TPAN/hearing/shrp_abstracts