Tonal strength of harmonic complex tones in machinery noise

Abstract

The sounds of machines often contain families of harmonically related sine waves that are referred to as harmonic complex tones. The perceived tonal strength of these types of sounds can adversely influence people’s impressions of the sound. While a complex tone is comprised of many sine waves, usually only one prominent pitch sensation is produced. It can be argued that harmonic complex tones are perceived as a single entities, not as a sum of individual tones. A series of psychoacoustics tests was conducted to evaluate tonal prominence of harmonic complex tones. Two sounds of equal loudness were played to subjects. One was a harmonic complex tone in noise and the other was a single tone in noise. Subjects were asked to equalize the perceived tonalness of the two sounds by adjusting the tone to noise ratio of the single tone in noise. Tonalness and Terhardt’s pitch perception models were applied to the pairs of sounds used in each test. The feasibility of replacing harmonic complex tones with a tonally equivalent simple sound was investigated, and strong correlations between Aures’ tonality for the simple and complex tones were found.