The quest for quieter ventilation systems

Between the roaring of trucks in the street, the raised voices of neighbours and the hum of household appliances, many noises can affect our quality of life. However, measurement scales do not always fully capture how people perceive them. Joonhee Lee, an associate professor in Concordia University’s Department of Building, Civil and Environmental Engineering, examined the noises emitted by ventilation and air-conditioning systems through the lens of psychoacoustics, a discipline that studies the relationship between human auditory perceptions and the sounds that reach our ears.

To better understand listeners’ reactions to noise, the researcher examined aspects other than the number of decibels or other criteria commonly used to assess noise. In fact, it is sometimes the tonality of a noise, i.e. the ability to clearly hear the “note” of the noise, that makes it annoying.

In a laboratory experiment reproducing a working environment, the researcher invited participants to take part in a moderately difficult cognitive exercise (a short mathematics test) while loudspeakers emitted noises. They were then asked to complete a questionnaire to indicate which noises had been the most disturbing and annoying.

This experiment led to the proposal of a model that adds two additional metrics to those usually used to assess whether a noise is annoying: frequency, measured in hertz, and tonality. These results can be used to develop new guidelines to add to those of the American Society of Heating, Refrigerating and Air-Conditioning Engineers.

Joonhee Lee would like to continue his work on equipping ventilation and air conditioning units with more efficient silencers, in collaboration with manufacturers.

References

Lee, J., et Wang, L.M. (2018). Development of a model to predict the likelihood of complaints due to assorted tone-in-noise combinations. The Journal of the Acoustical Society of America, 143(5), 108. doi: 10.1121/10.0000487

Lee, J., et Wang, L.M. (2020). Investigating multidimensional characteristics of noise signals with tones from building mechanical systems and their effects on annoyance. The Journal of the Acoustical Society of America,147(1), 108-124. doi.org/10.1121/10.0000487