Investigation of Two-Tone Interaction in Octave Complexes with the Help of the Pulsation-Threshold Method

Two pure tones with a frequency ratio 1 : 2, presented simultaneously to the ear, can give rise to effects on the loudness and the pitch of the higher-frequency component if their phase relation is varied. The phase effects have been investigated by the pulsation threshold method, in order to determine which test-tone frequency region contributes to the phase effects and what role two-tone non-linearity (“suppression”) plays. The results of the pulsation threshold experiments have been related to the variation of the loudness of the higher-frequency component, where the phenomenon of “loudness reduction” is encountered.

The results are discussed with reference to their consequences for the current explanations of the phase effects. Special attention has been given to the question of whether the phase effects might be the result of a vector summation of an aural harmonic present in the mechanical part of the auditory system and the higher-frequency component of the complex.