Extensive psychological experiments were carried out in this Part I on the consonance sensation of various dyad tones consisting of two components. As the frequencies of two componentsf1andf2(with an equal SPL) separate, the consonance gradually decreases down to the most dissonant point, whereafter it monotonically increases and mostly recovers at an octave separation. This consonance characteristic turned out to show a simpleVcurve if consonance is plotted against the frequency percent deviation in a logarithmic scale, and it suggests a dynamic and a static factor in consonance perception. The most dissonant frequency deviation is approximately 10% atf1=440 Hz, and it increased with sound pressure and frequency, but it was not simply proportional to the critical bandwidth. For dyads whose two components have different sound‐pressure levels (SPLs)L1andL2, the consonance differs with spectrum forms, even when the level difference is the same. A dyad with a spectrum form (P1>P2,f1