Modeling the interaction between the hearing protector attenuation function and the hearing loss profile on sound detection in noise
Invited paper
University of Ottawa
Wednesday 3 june, 2015, 10:40 - 11:00
0.4 Brussels (189)
Abstract:
Hearing protectors with a flat or nearly uniform attenuation across
frequency maintain the spectral balance of workplace sounds and are often
recommend when, in additional to protection, good signal audibility, speech
communication and auditory situational awareness are essential. Such
protectors have been especially indicated for wearers with high-frequency
hearing loss to maintain audibility at all frequencies. However, few studies
are available on the specific merits of flat/uniform protectors and
relatively little is known on the exact conditions when such devices can be
beneficial. Furthermore, while such devices are described in some acoustical
standards, the definition of flatness is generally unspecified, and even
when cited, the requirements have wide tolerances. This study reports on the
effects of the noise spectrum, hearing loss profile and shape of the
attenuation-frequency function on detection thresholds computed using a
psychoacoustic model of sound detection in noise. For normal-hearing users,
detection thresholds are found to be hardly affected by use of hearing
protectors, even in quite extreme conditions of low-frequency noise and
steeply increasing attenuation-frequency functions. With aging and noise-
induced hearing loss, sound detection in noise above 2500 Hz becomes
progressively more sensitive to the slope of the attenuation function as
well as to the overall protected level achieved. Shallower slopes are
warranted for individuals with moderate-severe hearing loss to limit the
upward spread of masking in low-frequency noise, while controlling the
amount of attenuation at high frequencies prevents excessive elevation of
absolute thresholds. Further work is needed to quantify the benefits of
flat/uniform hearing protectors in more complex tasks and other auditory
dimensions such as speech communication, sound quality and the
interpretation and recognition of important sounds in one’s environment.