Psychological responses to low-level transient sounds in background sounds generated by an air conditioner

Although air conditioners are installed extensively in buildings to achieve thermal amenities over extended periods, they are considered as one of the primary noise sources in buildings. Air conditioners mostly generate sounds that remain constant over time, and the sound quality of these steady sounds has been evaluated in several studies. However, these appliances occasionally generate low-level transient sounds that disturb the users during sleep or at other times when they require silence. This study aimed to determine how users respond to low-level transient background noises generated by air conditioners and correlate their responses with existing physical factors. Subjective loudness, pitch, and annoyance were appraised using a paired comparison method. The A-weighted equivalent continuous sound pressure level (LAeq) and the factors evaluated using the autocorrelation function (ACF) were utilised to characterise low-level transient noises among several background sounds. Multiple linear regression analyses were performed using the statistical values of LAeq and ACF factors. The results revealed the following significant predictive variables used to assess subjective responses to low-level transient background sounds: the 10th percentile values of the delay time of the first maximum peak, width of the initial decay of the ACF, and the difference between the 10th percentile and 90th percentile values of LAeq and the amplitude of the first maximum peak. This suggests that pitch salience, spectral centroid, and the amount of level change can have significant effects on the user’s psychological response to low-level transient sounds among background sounds.