The application of the equal energy hypothesis (EEH) to interrupted, intermittent, and time‐varying non‐Gaussian noise exposures

Abstract

Industrial data and animal research show that non‐Gaussian (nonG) noise exposures are more hazardous to hearing than energy equivalent Gaussian (G) exposures. A statistical metric, kurtosis [b(t)], was shown to order the severity of noise‐induced trauma following a nonG exposure relative to an energy and spectrally equivalent G exposure. Four groups of chinchillas were exposed to one of four different nonG interrupted, intermittent, and time‐varying (IITV) noise paradigms over 19 days at an Leq=103 dB(A) SPL, with b(t)=25 or 50. Each daily exposure consisted of two 4.25‐h periods with an hour break. Each 4.25‐h exposure was interrupted for 15 min and each 5‐day sequence was separated by a 2‐day break. Each daily IITV exposure followed one of two different SPL temporal patterns that varied between 90 and 108 dB(A). All IITV exposures produced a toughening effect that did not alter the degree of noise‐induced trauma. NonG noise produced as much trauma as a G exposure at 110 dB. Despite very different temporal paterrns for the b(t)=50 exposures, trauma was the same. Thus within a common class [i.e., the same Leq and b(t)] of nonG, IITV exposure, the EEH may apply. [Work supported by NIOSH.]