A Contribution to the Physiology of the Perilymph Part III: On the Origin of Noise-Induced Hearing Loss

Abstract

After exposure to white noise (SPL > 90 dB) the cochlear half life (τ) is increased by 100%. After exposure to white noise (90 dB<SPL<105 dB) the concentration of lactate in the perilymph increases significantly, while the blood level remains constant. Both results are capable of supporting the hypothesis that exposure to noise of a critical intensity (which appears to lie beween 90 and 100 dB) reduces cochlear blood flow. This reduction in turn diminishes the exchange rate of perilymph and reduces the oxygen supply to the sensory cells. The subsequent hypoxidosis of the organ of Corti may cause metabolic breakdown in, and on prolonged exposure, degeneration of the sensory cells. Both results are further capable of supporting the hypothesis outlined in Part I, that perilymph is the medium of transport to and from the cells of the organ of Corti.