Summary

Noise and vibrations daily affect hundreds of thousands of Quebec workers. Exposure to excessive noise contributes to isolation and reduces coordination and concentration, increasing the risk of accidents and deafness. Vibrations can be transmitted to the human body through the use of vibrating tools or driving vehicles in adverse conditions. They can then generate pathologies that handicap the affected person. Noise and vibrations are forms of pollution that can alter workers’ health, reduce productivity and cause absenteeism. In other words, noise and vibrations generate significant human, social and economic costs.

In many Quebec industries, including mining, construction, metals processing, forestry, agriculture, aerospace, policing etc., noise and vibrations often result from rapid or short-lasting phenomena (loud impulse noises, shocks and impacts from percussive tools, riveting, nailing, drilling, explosions, etc.). Modelling tools have been developed to help reduce noise and vibrations in the workplace. However, these are frequency models that work well for continuous, stationary phenomena, but cannot effectively handle transient or impulse phenomena. Models designed in the time domain would be more appropriate for such phenomena because they could be used to solve wave propagation and elastodynamic equations directly in time, in principle without simplifying approximations. Such models could also be used to analyze non-linear phenomena which cannot be effectively handled by frequency methods.

This project involves a bibliographic study of temporal modelling tools and documents their occupational health and safety applications, more specifically in reducing transient or non-linear impulse noise and vibrations. The literature review covered close to 200 documents.

In the first part, the fundamentals of temporal methods were explained. They were described in general and various resolution methods were presented. Two broad resolution classes were detailed: methods developed directly in the time domain, and those that use transformations in the Laplace or Fourier domains. The pros and cons of these various methods were reported, along with a description of how they differ from and complement frequency methods. A non-exhaustive inventory of calculation codes based on temporal methods was also compiled.

The second part of the study served to identify existing applications based on temporal methods in occupational health and safety. The review first focused on applications related to hearing protectors and to auditory systems subject to impulse noise. Next, applications related to non-linear phenomena and transient phenomena resulting from impulse noise, shocks and impacts were identified. Lastly, temporal methods were used to characterize porous materials for optimal usage in transient conditions. It was noted that existing applications reveal the immense potential of temporal methods, but these still seem to be very little used for concrete noise and vibration issues in occupational health and safety (OHS).

In light of the study, it would be worth testing a number of commercial temporal modelling programs to evaluate their actual performance in resolving vibroacoustic issues generated by impulse noise in OHS. The test results could be used to assess the relevance of acquiring appropriate temporal modelling tools to eliminate or reduce loud noises and strong vibrations in the workplace. Digital tools would help researchers accurately predict and improve the effectiveness of hearing protectors subject to loud impulse noise, and help reduce noise and vibrations produced by percussive tools through the use of better characterized porous and viscoelastic materials.