Results of the National Institute for Occupational Safety and Health—U.S. Environmental Protection Agency Interlaboratory Comparison of American National Standards Institute S12.6-1997 Methods A and B

• Published in: The Journal of the Acoustical Society of America Vol. 125; no. 5; pp. 3262 - 3277
• Main Authors: Murphy, William J., Byrne, David C., Gauger, Dan, Ahroon, William A., Berger, Elliott, Gerges, Samir N. Y., McKinley, Richard, Witt, Brad, Krieg, Edward F.
• Format: Journal Article
• Language: English
• Published: Melville, NY Acoustical Society of America 01.05.2009; American Institute of Physics
• Subjects: Algorithms; Analysis of Variance; Anthropometry; Applied physiology; Auditory Threshold; Biological and medical sciences; Ear Canal - anatomy & histology; Ear Protective Devices; Ergonomics. Work place. Occupational physiology; Female; Guidelines as Topic; Head - anatomy & histology; Hearing; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Male; Medical sciences; National Institute for Occupational Safety and Health (U.S.); Prosthesis Fitting - methods; Reproducibility of Results; United States; United States Environmental Protection Agency - legislation & jurisprudence; United States; USA, New York; Occupational exposure; Standards; Environmental protection
• ISSN: 0001-4966; 1520-8524; 1520-8524
• DOI: 10.1121/1.3095803

The National Institute for Occupational Safety and Health and the Environmental Protection Agency sponsored the completion of an interlaboratory study to compare two fitting protocols specified by ANSI S12.6-1997 (R2002) [(2002). American National Standard Methods for the Measuring Real-Ear Attenuation of Hearing Protectors, American National Standards Institute, New York]. Six hearing protection devices (two earmuffs, foam, premolded, custom-molded earplugs, and canal-caps) were tested in six laboratories using the experimenter-supervised, Method A, and (naïve) subject-fit, Method B, protocols with 24 subjects per laboratory. Within-subject, between-subject, and between-laboratory standard deviations were determined for individual frequencies and A-weighted attenuations. The differences for the within-subject standard deviations were not statistically significant between Methods A and B. Using between-subject standard deviations from Method A, 3–12 subjects would be required to identify 6-dB differences between attenuation distributions. Whereas using between-subject standard deviations from Method B, 5–19 subjects would be required to identify 6-dB differences in attenuation distributions of a product tested within the same laboratory. However, the between-laboratory standard deviations for Method B were −0.1to3.0dB less than the Method A results. These differences resulted in considerably more subjects being required to identify statistically significant differences between laboratories for Method A (12–132 subjects) than for Method B (9–28 subjects).