In-depth survey report: comparison of two acoustic test fixtures for measurement of impulse peak insertion loss.
Khan A; Fackler CJ; Murphy WJ
Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB 350-13a, 2013 Nov; :1-34
In 2012, NIOSH partnered with 3M and VIAcoustics for a field study at the 3M(TM) E-A-RCAL Laboratory (Indianapolis, Indiana) to measure Impulse Peak Insertion Loss (IPIL) with four hearing protector conditions. IPIL characterizes the noise reduction provided by a hearing protection device in response to high-level impulse signals. The IPIL value is the difference between the maximum sound pressure levels in open-ear and closed-ear conditions. Two data acquisition systems gathered readings from a blast probe and two models of the same acoustic test fixture (ATF): one model from E-A-RCAL and one from NIOSH. The ATFs and blast probe were placed in front of a horn attached to an acoustic shock tube, which produced acoustic impulses at various test levels. Four hearing protection devices [3M(TM) E-A-R(TM) Single-Ended Combat Arms(TM) Earplug, Etymotic Research ETYPlugs Earplug, 3M(TM) Peltor(TM) TacticalPro Communications Headset, and a dual-protector ETYPlugs earplug with TacticalPro earmuff] were evaluated at nominal peak impulse levels of 132, 150, and 168 decibels (dB). The data were simultaneously recorded by two acquisition systems and did not differ significantly between systems. However, statistically significant differences were observed between the IPIL estimates from the E-A-RCAL and NIOSH ATFs and between the left and right ears of each ATF. The IPIL measured by the left ear of the E-A-RCAL ATF was significantly higher than that of the right ear. The NIOSH ATF did not show such trends, even though the two ATFs were nearly identical. The orientation and location of the ATFs with respect to the wavefront expanding from the horn were significant factors on the impulse level at the two fixtures and between the ears of the fixtures. For the majority of the protectors and impulse levels, the differences between the average IPIL measurements for the two ATFs were statistically significant, indicating real differences possibly due to the fixtures' position or construction. To ensure repeatability, the IPIL estimates were computed with two separate implementations of the ANSI/ASA S12.42-2010 standard. Analyzing the full-length waveforms recorded during the study with the NIOSH MATLAB IPIL calculator and the VIAcoustics IPILA software yielded identical IPIL estimates.
Control-technology; Engineering-controls; Noise; Noise-exposure; Ear-protection; Ear-protectors; Hearing-protection; Personal-protective-equipment; Equipment-design; Equipment-reliability; Laboratory-testing; Impulse-noise; Noise-measurement; Standards; Testing-equipment; Noise-levels; Auditory-discrimination; Acoustic-signals; Acoustic-vibration; Acoustical-measurements; Measurement-equipment; Performance-capability; Noise-waves; Noise-control; Hearing-tests; Shock-waves; Sound-attenuation;
Author Keywords: Impulse Noise; Hearing Protection Devices; Noise induced hearing loss; American National Standards Institute; Noise Reduction Rating
Field Studies; Control Technology
NTIS Accession No.
National Institute for Occupational Safety and Health