A Pilot Study on the Effects of Hearing Protection and Ambient Noise Characteristics on Intensity of Uttered Speech.
Casali-JG; Horylev-MJ; Grenell-JF
Trends in Ergonomics/Human Factors IV, Proceedings of the Annual International Industrial Ergonomics and Safety Conference, Miami, Florida, 9-12 June, 1987 1987:303-310
A pilot study was carried out in 4 males and 4 females, aged 22 to 30 years, to determine the effects of earmuff occlusion, environmental noise and noise spectrum, on the levels of uttered speech intensity, in order to obtain base line data for a large study regarding the speech communication problems encountered in noise environments by workers provided with hearing protection. Use of hearing protection devices (HPDs) reduced the user's voice intensity level as compared to an unoccluded condition, with a mean voice reduction of 4.2 A-averaged decibels (dBA) across all ambient noise conditions. Regardless of the use of hearing protection, at levels of noise increasing from low to moderately high, the voice intensity of the speaker increased at a rate equal to one half the rate of the increase of the noise. Speech intensity level increased on average from 7.3.2dBA in 60dBA noise to 82.0dBA in 83dBA noise. The use of hearing protectors in a quiet environment appeared to increase the voice level of the wearer, while at moderately high levels of noise the use of a protective device resulted in the gradual decrease in the level of the wearer's voice, as compared to failure to wear such a device. The increase in vocal level by unoccluded subjects was twice as great as in occluded subjects. The presence of significant low frequency sound intensity in the spectrum of the ambient noise accounted for a higher level of compensation in the speaker's voice, as compared to spectra free of low frequency sound intensity. The authors suggest that this effect is due to interference with the speakers own voice level feedback by the effects of upward masking and pronounced bone conduction with low frequencies.
NIOSH-Grant; Noise-control; Ear-protectors; Speech-transmission; Noise-levels; Hearing-threshold; Occupational-health; Voice-communication; Personal-protective-equipment;
Indus Engr and Operations Res VA Polytechnic Inst & St Univ Human Factors Laboratory Blacksburg, VA 24061
Control Technology and Personal Protective Equipment; Research Tools and Approaches;
Trends in Ergonomics/Human Factors IV, Proceedings of the Annual International Industrial Ergonomics and Safety Conference, Miami, Florida, 9-12 June, 1987
Virginia Polytechnic Inst and St Univ, Blacksburg, Virginia