Relationship between attenuation characteristics of hearing protectors and speech intelligibility in noise
Masahiro HASHIMOTO1
Abstract:
In industrial workplaces, it is widely believed that the use of hearing
protectors interferes with speech communication and with the perception of
warning signals. The objective of this study was to evaluate the effect of the
attenuation of hearing protectors on speech perception in noise. In the
experiment, the intelligibility of Japanese sentences presented at two speech
levels (65 and 85 dBA) in pink noise was assessed for ten normal-hearing adults,
using three protectors with different attenuation characteristics. The noise
level was altered at signal-to-noise ratios (SNR) of 0, +5, and +10 dB. The
results showed that speech intelligibility was significantly influenced by type
of protector, speech level, and SNR. The interaction between these factors was
statistically significant. In general, the wearing of the earplug with decreased
low-frequency attenuation did not help to improve the intelligibility of speech
presented in noise. Correlations between the average attenuation for a specific
frequency range and the speech intelligibility were poor, indicating that the
attenuation characteristics of the protectors have little effect on speech
intelligibility in noise. These results imply that a reduction in the
attenuation should not be considered as a countermeasure against the problems of
speech communication with hearing protectors.