The description of fan noise by indexes based on the specific loudness

Abstract

In a previous study of the authors, a broad variety of fan sounds that were equalized in overall A-weighted level was rated in listening experiments with a semantic differential. The factor analyses of the ratings indicated six perceptual dimensions and five groups of sounds, which shows the rich variety of sound characteristics covered by the tested fan sounds. The results showed that the groups of pleasant and unpleasant sounds differed mainly with respect to the first three perceptual dimensions, “pleasant,” “humming/bass,” and “shrill.” An analysis of the specific loudness according to the DIN 45631 standard revealed systematic differences in the specific loudness patterns for the different groups of fan sounds. It was possible to define two psychoacoustic indexes that correlate highly with the factor values of the three most important perceptual dimensions of fan noise. The most important index, Nratio, relates the amount of loudness resulting from low mid-frequency content between 2 Bark and 5 Bark to the loudness from high frequency content above 10 Bark. The identified boundaries of the frequency ranges employed in the indexes are in good agreement with those found for air conditioning noise, air cleaners and in the context of sound masking in offices.