Summary It is quite likely that hundreds of thousands of Quebec workers are regularly exposed to very high levels of noise and vibration in the workplace. These hazards are associated with occupational injuries that may be irreversible over the long term. High levels of noise and vibration can therefore have very significant human, social and economic costs. For that reason, robust prevention initiatives are required to limit worker exposure to these health risks. In a range of occupational sectors, including mining, construction, metals processing, forestry, agriculture, aerospace and policing, noise and vibration are often impulse hazards, meaning they generally occur at very high levels for short periods of time, during which they are potentially very harmful to the workers exposed to them. An effective strategy for addressing these health risks should be based on time domain methods that can be used to describe the problems and solve them directly, instead of on frequency methods that, though widely available, are better suited to dealing with continuous, stationary and periodic phenomena. It would therefore seem appropriate to seek out time domain digital modelling tools that can be used to solve impulse noise and vibration problems, e.g., those concerning the portable tools that often generate the hazards, as well as those concerning the hearing protectors workers wear. The purpose of this study was to determine whether commercial modelling tools that offer time domain problem-solving techniques could advantageously be used to model impulse noise and vibration phenomena in occupational health and safety (OHS). More specifically, the solver modules in the time domain of the COMSOL, Abaqus and Virtual Lab software packages were tested to assess their suitability to deal effectively with two idealized impulse noise and vibration problems in connection with portable tools and hearing protectors. In the first part of the report, the real OHS problems related to portable tools and hearing protectors are described and put into context. Levels of simplification for transforming these very real issues into idealized configurations more appropriate for software assessment are also explained, and the excitations considered are amply described. In the second part of the report, several approaches in the time and frequency domains are set out with a view to determining reference analytical solutions, which are then used to evaluate software performance. The third part is devoted, for each of the three software tools tested, to a substantive description of the foundations and modelling procedure, followed by the modelling approach per se to the idealized problems. The various criteria taken into account in the software evaluation are indicated. The fourth part of the report draws some comparisons, first between the results of the various approaches taken to assess the quality of the reference analytical solutions, and then between the reference solutions and the results obtained with the software tools. These comparisons showed that COMSOL and Abaqus delivered good results for the idealized portable tools problem, while for the hearing protector problem, the results of all three tools were generally acceptable. The fifth and last part of the report is devoted to the effective evaluation of the software tools, based on observations made about their use and the modelling results obtained. For each criterion considered, the evaluation entailed indicating the advantages and disadvantages of each tool. The conclusions of the evaluation were that (i) the tested versions of the time domain solver modules of the three software tools have the potential a priori to solve the real complex OHS problems of noise and vibration, only if porous treatments and nonlinearity in the propagation environment are not taken into account; (ii) the implementation of new formulations in the solvers of these modules is required to solve real complex OHS problems of noise and vibration.