Department of Vibroacustic Hazards - Projects
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Abstract

Studying the impact of the differences in combined characteristics of attenuation of hearing protectors on the efficiency of noise control.

Project manager: Jan Żera Ph.D.(Eng.), D.Sc. (Eng.)

Project summary:

The aim of the project was to study combined characteristics of attenuation of hearing protectors (amplitude and phase characteristics) and to determine the impact of the differences in these characteristics on the properties of hearing protectors protecting against impulse noise and amplitude and phase characteristics of the hearing protectors as a function of frequency.The project consisted in measurements of 22 earmuffs (Bilsom, Peltor, 3M, EAR, Opta and Frazer). Five subjects took part in those measurements. A measurement microphone was placed under the earmuffs worn by the subjects; MTW1 and MTW3 acoustic testers and KEMAR and Bruel&Kjaer acoustic manikins were used, too.A numerical model of a hearing protector was developed; its efficiency was tested. Numerical modelling was done with the measured amplitude and phase characteristics of earmuffs. The measurements were verified with audiometric measurements. This was done to determine to what degree the course of the measured amplitude and phase characteristics of earmuffs provide significant information on attenuating tonal components of noise.The study showed that attenuating tonal components of noise with earmuffs can be quite different from the mean values measured as attenuating noise in accordance with the recommendations of standard EN 24869-1. At the same time the usefulness of modelling in assessing impulse noise was proven.



Unit: Department of Vibroacustic Hazards

Duration: 01.01.2008 – 30.12.2010