Measurement of effective hearing protection device attenuation during a workshift in industrial plants Hugues Nélisse a Jérôme Boutin IRSST 505 Boul. De Maisonneuve Ouest Montréal, Québec, CANADA, H3A 3C2 Marc-André Gaudreau b Frédéric Laville c Jérémie Voix d Département de génie mécanique École de Technolgie Supérieure 1100 rue Notre-Dame Ouest Montréal, Québec, CANADA, H3C 1K3 ABSTRACT Discrepancies between labeled noise attenuation data measured in laboratory and field measurements data have been well documented for most types of hearing protection devices (HPD) throughout the years. High “laboratory” attenuation values lead to overestimation of most ratings used for the labeling of HPDs and, subsequently, can cause significant problems when trying to estimate the workers real-world protected levels. This paper presents a field study where un-protected, and protected levels as well as attenuation values were measured as a function of time for full workshifts in different noise environments, for different workers and different HPDs. The acquisition system, based on the F-MIRE technique, is presented. This system was specifically designed to be able to record the un-protected and protected signals at workers ears in a continuous manner using miniature microphones inserted through the HPDs. The system was also designed to be lightweight, comfortable and rugged enough to be able to be worn by workers with minimal disturbance of their working habits. Time data were obtained which allow one to follow the evolution of protection and noise levels as a function of time and to carry out complete signal analysis. Examples of results for different noise environments and different workers are presented and discussed. a Email address: nelisse.hugues@irsst.qc.ca b Email address: gaudream@cdrummond.qc.ca c Email address: Frederic.Laville@etsmtl.ca d Email address: jvoix@jerevox.com