Response to air-cooling machinery noise: A preliminary study

Abstract

People living close to commercial properties are often exposed to air-cooling machinery noise. Of primary concern is the awareness of tones in the sounds and how that awareness contributes to the overall annoyance experienced by people exposed to the noise. For noise control, it is most straightforward to control the strength of tonal contributions from components such as fans and compressors. For the class of machinery considered in this study, fan fundamentals are usually around 60 Hz and compressor fundamental frequencies are typically between 500 and 700 Hz. A preliminary study was carried out using 27 sounds that simulated a broad range of possible noises made by this type of air-cooling machinery. The sounds were presented to people who were asked to rate them in terms of tonality and annoyance. Tonality and annoyance ratings only increased when sounds contained at least one compressor tone above a certain threshold level. High correlations were found between objective metrics and the average of the subjects’ responses. Recommendations for future research include investigations into the individual effects of changing spectral balance, overall loudness, and tonal contributions for these types of sounds, because changing tonal levels alone affects all of these sound characteristics simultaneously.