Uncertainty calculation for noise attenuation measurements of hearing protectors

Abstract

The objective of this paper is to present a metrology study necessary for accreditation of the Industrial Noise Laboratory (LARI) at The Federal University of Santa Catarina-Brazil for hearing protector noise attenuation procedures using the Real Ear Attenuation at Threshold (REAT) method of the Brazilian National Institute of Metrology Standardization and Industrial Quality-INMETRO. A model for the calculation of measurement uncertainty was developed. The uncertainty calculation was based on the document, ‘‘Guide to expression of uncertainty in measurement,’’ by the International Organization for Standardization, first edition, corrected and reprinted in 1995, Geneva, Switzerland. The uncertainty of each source of error was estimated. The overall uncertainty of the noise attenuation measurement of hearing protectors was calculated for each 1/1 octave band frequency test and the results applied in the single number (NRRSF—noise reduction rating for subject fit) uncertainty calculation. It was concluded that the largest uncertainty is due to the determination of the subject’s hearing thresholds.