Summary

Globally, noise is an increasingly important and widespread concern. According to the World Health Organization, approximately one in four people worldwide will suffer from a hearing deficit to some degree by 2050. In many countries and regions of the globe, noise is the second-greatest environmental factor triggering health problems, after air pollution.

From a cognitive or perceptual perspective, environmental noise can disrupt sleep and impair learning at school, for example. In the workplace, it can impede proper understanding or perception of signals or messages. Moreover, a major consequence related to noise exposure in the workplace is occupational hearing loss, which is among the most common occupational illnesses. All public health studies show that the number of cases of occupational hearing loss caused by noise is still growing substantially, even though methods to prevent this illness are known (limit noise exposure, reduce the overall noise level). Decreasing the noise level makes it possible to reduce the number of cases of occupational hearing loss and the related costs, but also to limit this factor’s contribution to workplace accidents and to improve workers’ and other people’s quality of life.

The purpose of this study is to better characterize the performance of sound-absorbing materials. The performance of a soundproofing treatment is expressed by its absorption coefficient, which falls theoretically between a value of 0 (non-absorbing material) and 1 (perfectly absorbing material). The methods used under current standards show highly variable results among different test laboratories, and the absorption coefficients obtained frequently achieve non-physical results (i.e., values greater than 1).

This study follows up on a previous study (Robin et al., 2018) concerning the assessment of a robust, reliable characterization of sound-absorbing treatments in the laboratory, which was carried out on a prototype, non-automated testbench. Despite its many positive contributions (absorption coefficients that do not exceed 1, ability to characterize small samples), the main limitation of this method related to the low-frequency range, where it remained inaccurate.

First a measuring station was developed, which made it possible to limit measurement errors and automate the measurement cycle. In addition to the previous method, two new approaches for calculating the absorption coefficient were developed and an existing approach from the literature was tested. The method proposed in the previous study and used with the new automated measuring station still shows some limitations in the low-frequency range.

This was also true of the existing method from the literature. Nevertheless, the results obtained with the two new approaches enabled us to overcome the low-frequency limitations observed with the earlier method. In addition, they made it possible to combine different experimental, and numerical, approaches.

Overall, the results obtained show that the combination of an automated measuring station and different approaches is better able to measure, or numerically calculate, the absorption coefficient of soundproofing materials and thus to apply and size them to reduce workplace or environmental noise. This raises the possibility of a robust, interesting alternative to the existing standard methods (impedance tube, live room). The measuring station developed will be available at the ICAR (ÉTS-IRSST Common Infrastructure for Research in Acoustics) laboratory and will be usable for other research on soundproofing materials, including their characterization.