Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part III. The validity of using subject-fit data

Abstract

The mandate of ASA Working Group S12/WG11 has been to develop ''laboratory and/or field procedure͑s͒ that yield useful estimates of field performance'' of hearing protection devices ͑HPDs͒. A real-ear attenuation at threshold procedure was selected, devised, tested via an interlaboratory study, and incorporated into a draft standard that was approved in 1997 ͓J. D. Royster et al., ''Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part I. Research of Working Group 11, Accredited Standards Committee S12, Noise,'' J. Acoust. Soc. Am. 99, 1506-1526 ͑1996͒; ANSI S12.6-1997, ''American National Standard Methods for Measuring Real-Ear Attenuation of Hearing Protectors'' ͑American National Standards Institute, New York, 1997͔͒. The real-world estimation procedure utilizes a subject-fit methodology with listeners who are audiometrically proficient, but inexperienced in the use of HPDs. A key factor in the decision to utilize the subject-fit method was an evaluation of the representativeness of the laboratory data vis-à-vis attenuation values achieved by workers in practice. Twenty-two field studies were reviewed to develop a data base for comparison purposes. Results indicated that laboratory subject-fit attenuation values were typically equivalent to or greater than the field attenuation values, and yielded a better estimate of those values than did a͒ This paper is the last of three parts of a body of work that represents the research and analyses of S12/WG11 in conjunction with the development of ANSI S12.6-1997. Part I appeared in 1996 in J. Acoust. Soc. Am. 99, 1506-1526 ͑1996͒. It referenced two succeeding parts, one of which Part II is still in press and hence will appear out of chronological order. Additionally the advance citation of this paper in Part I, listed the first two authors in the reverse order from that which appears above. b͒ ''Selected research articles'' are ones chosen occasionally by the Editor-in-Chief that are judged ͑a͒ to have a subject of wide acoustical interest, and ͑b͒ to be written for understanding by broad acoustical readership.665 665

Health hazard evaluation report: evaluation of impact and continuous noise exposure, hearing loss, heat stress, and whole body vibration at a hammer forge company.

“…However, our testing of the attenuation for these hearing protectors in the mannequin head and the range of attenuation achieved by subject fit testing show that more noise attenuation than the manufacturers' NRR may be possible with well-fitting hearing protectors. In contrast, subject fit test data also show that poorly fitting hearing protection provides attenuation much worse than the manufacturers' reported NRR [Berger et al 1996;Berger et al 1998;Franks et al 2000;Joseph et al 2007;Murphy et al 2011]. …”

Hearing Protectors: Topicality and Research Needs

“…These tests result in a so-called subject fit (SF) attenuation value. This method is proven and appears to give attenuations closer to real-world ones [31]. U.S. standards have subsequently been transposed into ISO/TS 4869-5:2006 [32].…”

Advanced hearing protector study conducted at: General Motors Metal Fabricating Division Flint Metal Center - Flint, Michigan, January 2004 - February 2005 (revised).

“…Several excellent review articles on this topic have been written. 13,14,15,16 Recently, a report on the measurement and rating of hearing protection devices was drafted for the EPA. 17 This report followed the convention of examining the attenuation ratings where the lower ratings represent what a certain percentage of users would achieve.…”