You are invited to attend Charlene Chang’s Master’s thesis defense

When: Wednesday, April 22nd, 2020 12:30 noon
Where: Virtual-Canvas-Audi Student Resources- Collaborative Ultra or
Title: “Electrocochleography as a Diagnostic Tool for Noise-Induced Cochlear Synaptopathy”
Candidate: Shiang Ling (Charlene) Chang
Committee: Navid Shahnaz, Tony Herdman, and Sasha Brown


Purpose: Recent studies suggest synaptic connections between hair cells and the auditory nerve may be more vulnerable to noise exposure than the sensory hair cells in the cochlea. The resulting neuropathy may be associated with a decreased performance with speech in noise despite a normal audiogram. This type of hearing loss has been named “hidden hearing loss”. Studies with animal models suggest that suprathreshold wave I auditory brainstem responses are sensitive to the loss of synaptic ribbons in mice, but humans studies are inconclusive. This work aims to identify the diagnostic potential of tympanic membrane electrocochleography on noise-induced cochlear synaptopathy.


18 music students (n = 32; mean age = 21.7) with normal hearing (≤ 25 dB, HL 250-8000 Hz) and 19 normal hearing controls (n = 35; mean age = 22.5) were recruited. Lifetime noise exposure and tympanic membrane electrocochleography with 95 dB nHL clicks were recorded. A factorial ANOVA was used to investigate the effect of music background and gender on the lifetime noise exposure. Mixed model ANOVA was used to analyze effect of noise exposure, gender, and ear on absolute SP and AP amplitudes, SP/AP amplitude ratio, and SP/AP area ratio.


There was a trend for higher lifetime noise exposure in music students but it did not reach significance. There were no significant group differences on any of the electrocochleography measures.


In the present study, there is no evidence for electrophysiological measures associated with noise exposure. The use of tympanic membrane electrocochleography to assess cochlear synaptopathy in humans remains inconclusive. It is possible that the effects of noise exposure may be observed in individuals with greater lifetime noise exposure than the cohort tested within this study. Additional research would be needed to develop a test protocol that can diagnose peripheral cochlear damage preceding sensory hair cell loss in humans.