An evaluation of four selected ear protectors
Delorier, Joseph R.
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The primary purpose of the present investigation was to evaluate three insert ear protectors and one semi-insert ear protector for the amount of sound attenuation offered by each device. The ear protectors were also evaluated subjectively by the subjects for comfort of fit and for effectiveness of attenuation. A further goal of the present study was a critical review of the method for determining the sound attenuation of ear protectors as specified by the American National Standards Institute (ANSI). For each of the ten normal-hearing male subjects, three test thresholds (with ear protection) for each ear protector, as well as three reference thresholds (without ear protection), were obtained in a soundfield test situation. The amount of attenuation for an ear protector for each trial was the difference between reference and test thresholds. The total amount of attenuation for a specific ear protector was the average of the three trials for the ten subjects. The subjects evaluated the ear protectors subjectively for comfort of fit by ranking the protectors from one (1) to four (4), with a rank of one (1) indicating the most comfortable ear protector, and a rank of four (4) indicating the least comfortable ear protector. The same rank-ordering procedure was followed for obtaining the subjects' opinions concerning the effectiveness of attenuation of the ear protectors. The results of an analysis of variance revealed that there was no significant overall difference among the four ear protectors in regard to the amount of attenuation offered by the devices. However, a Newman-Kuels method of multiple comparisons revealed that there were differences among certain ear protectors at specific test frequencies. A Friedman test performed on the ranked data for comfort revealed that the subjects could determine differences in the comfort of the four ear protectors. The subjects were unable, however, to rank the ear protectors for effectiveness of attenuation. It was concluded that, although ear protectors should be evaluated for sound attenuation, other factors (cost, comfort, nontoxicity, etc.) should also be investigated to determine the acceptability of an ear protector for a specific hearing conservation program. After critically reviewing the ANSI Standard for evaluating ear protectors, three possible modifications to the standard were suggested. These included: (1) the addition of methods for evaluating ear protectors by factors relating to the acceptability of the protectors to the wearer, (2) the specification of an exact or more precise psychophysical or audiometric technique for obtaining the threshold data, and (3) the adoption of a one-trial measurement procedure instead of the required three-trial procedure for evaluating a specific set of ear protectors.