Extensive hearing loss induced by low-frequency noise exposure.

Background: With little attention given to low-frequency traffic noise and our understanding that cochlear function may be highly susceptible to low-frequency noise, there is an urgent need to determine traffic noise-induced hearing loss (NIHL), not only the hearing loss at low frequency but also the possible high-frequency hearing loss. Methods: The current study aims to investigate the potential for extensive hearing loss induced by exposure to 0.063 kHz octave band noise (OBN), which is an important component of low-frequency traffic noise. The threshold of auditory brainstem response (ABR) was used to evaluate hearing function before and after noise exposure. Chinchillas were randomly assigned into seven different groups. Group 63-3 h/6 h, Group 2 k-3 h/6 h, and group 4 k-3 h/6 h were exposed for either 3 or 6 h to 0.063, 2, and 4 kHz OBN at 90 dB SPL, respectively. The control group was not exposed to noise. Results: Significant ABR threshold-shifts (TS) were observed at 0.88, 2, 4, and 5.7 kHz in Group 63-6 h, and at 2.8 and 4 kHz in Group 2 k-6 h, and at 5.7 kHz in Group 4 k-6 h. ABR-TS were consistent with outer hair cell (OHC) losses, exposure to 0.063 kHz OBN at 90 dB SPL for 6 h induced large-scale losses of OHC both in low- and high-frequency region. Conclusions: Exposure to 0.063 kHz low-frequency OBN at 90 dB SPL for 6 h leads to significant hearing loss over an extensive range from low to high frequencies.