Sound quality evaluation of air-conditioner noise based on factors of the autocorrelation function

The aim of this paper is to clarify the characteristics of air-conditioner noise and determine the factor that is most influential on the subjective annoyance caused by this noise. The A-weighted equivalent continuous sound pressure level (LAeq) and factors extracted from the autocorrelation function (ACF) were analyzed. Subjective annoyance was evaluated using a paired comparison method. Multiple regression analyses were performed using a linear combination of LAeq, the ACF factors, and their standard deviations (SDs). The results indicated that the noise characteristics caused by each air conditioner and each operating level are determined by LAeq, and by the width of the first decay of the ACF, Wϕ(0), which corresponds to the spectral centroid. The multiple regression analyses indicated that the total subjective annoyance caused by air-conditioner noise can be predicted using the delay time and amplitude of the first maximum peak of the ACF (τ1 and ϕ1) and the SD of ϕ1. Annoyance was found to increase with decreasing τ1 and ϕ1, and with increasing ϕ1 SD, suggesting that noise components with higher pitches, weaker pitch strengths, and larger pitch strength variations cause greater levels of annoyance.