Systematic Evaluation of the Relationship Between Subjective and Objective Measurement Methods of Hearing Protector Devices Attenuation

Invited paper

Hugues Nélisse


Wednesday 3 june, 2015, 11:00 - 11:20

0.4 Brussels (189)

Despite numerous efforts to control and reduce noise sources, hearing protector devices (HPD) are still widely used in the workplace in an attempt to reduce or limit noise-induced hearing loss. Hearing protectors come in various types and sizes (earmuffs or earplugs) and may offer different functionalities (active/passive attenuation, communication, etc.). A key component when selecting a HPD is the noise attenuation offered by the device. The subjective Real-Ear Attenuation at Threshold (REAT) test method is the most common procedure to measure attenuation of a HPD and is considered the “gold standard”. On the other hand, with the increase popularity of individual fit testing and miniaturization of electronic components, the Microphone-In-Real-Ear approach (MIRE) is becoming more appealing and well suited for estimating HPDs attenuation both in laboratory and in “real world” occupational conditions. In this approach, two miniature microphones are used to simultaneously measure the sound pressure levels in the ear canal under the hearing protector, as well as outside of the protector. This paper aims at presenting a systematic evaluation of the various factors relating the subjective and objective attenuation values. Experiments on several human subjects were carried out where the subjects were instrumented on both ears with miniature microphones outside and underneath the protector. They were then asked to go through a series of subjective hearing threshold measurements followed by objective microphone recordings using high level diffuse field broadband noises. Earmuffs, earplugs and double-protection were tested for each subject and attenuation values were compared. The various factors relating the subjective REAT values to the objectives attenuation data are first presented. Results showing the importance of these factors are presented and discussed as well as various comparisons obtained with the different attenuation values.

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