Attenuation measurements of ear muffs at Falconbridge Limited, Canadian Nickel Division, Sudbury Operations, 1984

Abstract At the Falconbridge Limited, Canadian Nickel Division, Sudbury Operations, we investigated the "NO NOISE" ear muffs model NN3-F which is a Swedish product with foam-filled sealing rings (the Hellberg Standard Volume Hearing Protector). It is used extensively at Falconbridge mines in Sudbury.
The research which was carried out in the four Falconbridge mines was conducted under three different headings: manufacturer's attenuation data (psychophysical method), clamping force and head size (bizygomatic diameter), and attenuation tests (physical methods) under working conditions.
Manufacturers of hearing protectors claim their products offer noise reductions of 23 decibels (NRR) or more, but they fail to point out that this reduction is obtainable only under ideal conditions. The reality of attenuation under working conditions, as several studies have found, is quite different.
Methods for using short measurements to determine the noise exposure index, and for controlling muff-wearing habits, were developed at the Elliot Lake Laboratory. Measurements taken at Falconbridge on "NO NOISE" ear muffs revealed that they have a practical attenuation of some 10 to 13 decibels. It is important to note here that measurements also revealed that clamping force (thus attenuation) was in an inverse relationship with ear muff comfort. Measuring attenuation using noise dosimeters was a difficult job. Not a single surveyor would accept these measurements (physical method) for absolute accuracy. Apart from that, it was impossible to measure, in one
Keywords: Mine safety, Attenuation, Ear muffs, Noise, Clamping force, Head size, Falconbridge Limited.
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Author(s): PAUL DUFOUR, MICHAEL PARLEY
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