Hearing protector performance and standard deviation.

The attenuation performance of a hearing protector is used to estimate the protected exposure level of the user. The aim is to reduce the exposed level to an acceptable value. Users should expect the attenuation to fall within a reasonable range of values around a norm. However, an analysis of extensive test data indicates that there is a negative relationship between attenuation performance and the standard deviation. This result is deduced using a variation in the method of calculating a single number rating of attenuation that is more amenable to drawing statistical inferences. As performance is typically specified as a function of the mean attenuation minus one or two standard deviations from the mean to ensure that greater than 50% of the wearer population are well protected, the implication of increasing standard deviation with decreasing attenuation found in this study means that a significant number of users are, in fact, experiencing over-protection. These users may be disinclined to use their hearing protectors because of an increased feeling of acoustic isolation. This problem is exacerbated in areas with lower noise levels.

Does the presentation of audiometric test data have a positive effect on the perceptions of workplace noise and noise exposure avoidance?

Research and 'common knowledge' has for many years accepted that education and feedback supplied to individuals during and immediately after workplace health assessments provides valuable information to workers about their health. Further, if more relevant and detailed information could be supplied then awareness and preventative action may increase proportionately. This research carried out with a rural Australian population has shown that preventative action did not increase in proportion to a corresponding increase in the amount and variety of information provided in connection with hearing health status. Two research groups underwent hearing tests, both with pure tone audiometry (PTA) while the second group also underwent otoacoustic emission (OAE) testing. Test results were presented to the subjects at the conclusion of their test session. An analysis of questionnaire responses at six week and twelve months follow up showed that more information did not result in increased preventative action. Barriers seem to exist such that individuals feel that they are not able to effectively act to reduce overall noise exposure. While self-efficacy initially increased, it declined to close to its initial value over the longer period. Other measures such as perceived susceptibility to hearing loss and the benefits of exposure reduction significantly increased and remained at the same increased level after twelve months. So, while overall awareness of noise and the risks of exposure were increased after both types of hearing test there was no increased hearing health benefit due to additional testing and hearing information.