Abstract
Research suggests that college-aged adults are vulnerable to tinnitus and hearing loss due to exposure to traumatic levels of noise on a regular basis. Recent human studies have associated exposure to high noise exposure background (NEB, i.e., routine noise exposure) with the reduced cochlear output and impaired speech processing ability in subjects with clinically normal hearing sensitivity. While the relationship between NEB and the functions of the auditory afferent neurons are studied in the literature, little is known about the effects of NEB on functioning of the auditory efferent system. The objective of the present study was to investigate the relationship between medial olivocochlear reflex (MOCR) strength and NEB in subjects with clinically normal hearing sensitivity. It was hypothesized that subjects with high NEB would exhibit reduced afferent input to the MOCR circuit which would subsequently lead to reduced strength of the MOCR. In normal-hearing listeners, the study examined (1) the association between NEB and baseline click-evoked otoacoustic emissions (CEOAEs) and (2) the association between NEB and MOCR strength. The MOCR was measured using CEOAEs evoked by 60 dB pSPL linear clicks in a contralateral acoustic stimulation (CAS)-off and CAS-on (a broadband noise at 60 dB SPL) condition. Participants with at least 6 dB signal-to-noise ratio (SNR) in the CAS-off and CAS-on conditions were included for analysis. A normalized CEOAE inhibition index was calculated to express MOCR strength in a percentage value. NEB was estimated using a validated questionnaire. The results showed that NEB was not associated with the baseline CEOAE amplitude (r = -0.112, p = 0.586). Contrary to the hypothesis, MOCR strength was positively correlated with NEB (r = 0.557, p = 0.003). NEB remained a significant predictor of MOCR strength (β = 2.98, t(19) = 3.474, p = 0.003) after the unstandardized coefficient was adjusted to control for effects of smoking, sound level tolerance (SLT) and tinnitus. These data provide evidence that MOCR strength is associated with NEB. The functional significance of increased MOCR strength is discussed.
Highlights
Noise-induced hearing loss (NIHL) remains a hearing health concern despite Occupational Safety and Health Administration standards for hearing protection and public health awareness campaigns
The present study showed that increased medial olivocochlear reflex (MOCR) strength can be found in non-musicians with high noise exposure background (NEB)
High NEB is associated with the increased MOCR strength in subjects with normal hearing sensitivity
Summary
Noise-induced hearing loss (NIHL) remains a hearing health concern despite Occupational Safety and Health Administration standards for hearing protection and public health awareness campaigns. Recent reports suggest that NIHL is no longer limited to industrial workers exposed to loud noise but is found in children, adolescents and college-aged young adults [6,7,8]. The college-aged adults are routinely exposed to damaging sound levels [4, 5]. Personal music players have been shown to exceed damaging sound pressure levels at high volume control settings [9]. Research on the auditory lifestyle of college students has shown that almost 50% were exposed to potentially harmful music, 44% used noisy equipment without hearing protection, and almost 29% of them worked in a noisy environment suggesting that the population might be susceptible to hearing loss and tinnitus [10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
