Audible changes mark when two sine tones enter the same critical band

Evidence

1 Critical bands by sine waves: Two sine waves are heard—one at a constant frequency (F1) of 440 Hz and th e second starting at 440 Hz, moving to around 660 Hz and back to 440 Hz. The changes described in Section 2.2 and illustrat ed in Figur e 2.6 should be audi ble. — David Howard, Jamie Angus, coustics and Psychoacoustics, 2952