Examining What Causes Perceived Dissonance in Musical Intervals and the Effect of Timbre on Dissonance

Dissonance is perceived when certain musical notes are heard simultaneously and create a harsh, clashing feeling. Consonance, the opposite of dissonance, is perceived as a pleasant harmony of musical notes. Timbre is the defining characteristic of sound which differentiates sounds from different sources. This study attempts to determine the cause of perceived dissonance and the effect of timbre on dissonance. We attempt to corroborate Hermann von Helmholtz’s theory of temporal dissonance, which proposes that dissonance results from beat frequencies created by interference of harmonic overtones. Our procedure examines algebraic and graphical representations of sound waves of the nine standard musical intervals from the minor second to the octave, produced on piano, ranging from dissonant to consonant. No clear correlations were found between different quantitative metrics and dissonance. The study also compares graphs of intervals from a piano and a human voice, which have different timbres. We noted that the graphs of piano notes, which have a “harder”-sounding timbre, had higher ratios of concavity changes to beat period than the graphs of sung notes, which have a “softer” timbre. Further research is planned to study whether graphical characteristics can reveal qualities of timbre.