Frequency Discrimination in a Simultaneous Two-Tone Signal

Discrimination of just noticeable change in pitch has been widely investigated. In contrast, works on discrimination of two simultaneous pitches produced by two tones have been scarce. In this work two methods were used to find the minimum frequency interval in a two-tone at which listeners perceive two distinct pitches. In the first, listeners tuned manually the frequency interval between components in a two-tone. In the second, the frequency interval between tones in a two-tone was switched between five different fixed values, and a pitch of a probe tone was compared with pitches in a two-tone. Both methods were used in two different groups of listeners, musicians and non-musicians. The first method yielded substantially narrower intervals. Both methods revealed that musicians were able to discriminate pitches at narrower intervals than non-musicians. The raw results of tests were evaluated by two approaches, one was based on fitting of the psychometric function and the other on statistical tests.