The Trill Threshold

Abstract

Two tones of different frequencies alternating successively 5 times/sec. were presented binaurally to human subjects. When the difference in frequency was small, the alternation sounded like a continuous up-and-down movement of the pitch. When the difference in frequency was large, the alternation sounded like 2 unrelated, interrupted tones. The transition point between these 2 perceptual organizations is called the trill threshold. The trill threshold was measured as a function of frequency. The magnitude of the difference in frequency between a fixed tone and a matching tone at the trill threshold varied directly with the frequency of the fixed tone.