Digital high-speed sampling of combined exposure to noise and vibration

The digital high-speed sampling technique was applied to simultaneous measurements of exposure to noise and vibration among workers who used hand-held power tools in a shipyard. The transducers were two accelerometers and two microphones which measured the transmission of vibration acceleration from the handle of the tool to the wrist and the attenuation of noise by the earmuffs. The measurements were taken by a microcomputer-controlled digital multichannel sampling unit. An analogue-digital converter was used with a 100-kHz scanner for multichannel signal acquisition in the 10 kHz bandwidth. The sound pressure was A-weighted, and the vibration acceleration was both unweighted and weighted according to the guidelines of the International Organization for Standardization. Impulsiveness was determined as the difference between the peak and root-mean-square levels. The noise exposure was 81 dB during grinding and 85 dB during hammering. The earmuffs provided protection against impulse noise at least when the impulses contained high frequencies. The transmission loss of vibration acceleration between the tool handle and wrist was 45 dB for grinding and 29 dB for hammering. The transmission of noise and vibration was affected by the frequency content and impulsiveness of the signals.