Perception of consonance about harmonious sounds

To date, many studies have been carried out with regard to the degree of harmony of a chord. As those studies have been based on the semitone of a Western musical scale, the case of very small frequency difference has not been investigated yet in detail. Not as music theory, but considering the application to a human interface etc., it is meaningful to investigate how small change of the frequency in a chord is recognized. Therefore, in the present study, we investigated on how the judgment of the consonance of a chord would be influenced when the frequency of one tone in a triad shifted slightly, lesser than 1/4 of the critical bandwidth. The stimuli were created by changing the major third or perfect fifth tones in the major triad chord by 2 Hz at a time. The participants were asked to choose the better harmony sound from the two stimulus sounds made into the pair. As just temperament is known to be a best consonance in the Western music, the sum of the frequency differences between the stimulus sound and just temperament was defined as the degree of dissonance. The relation between the dissonance and the degree of perceived harmony was investigated. The selection rate of the stimulus chord with fewer amount of change increased monotonously as the difference of the dissonance increased. It was clarified that the human could recognize the small frequency change of the triad as the decrease in harmony, and that the dissonance defined according to frequency difference is applicable for the evaluation of harmony. Furthermore, it was suggested that the music experts prefer the chord of equal temperament than that of just temperament.