Effect of Humming on Vision

Abstract

I WISH to comment on Rushton's article on humming and vision¹. If a cathode ray oscilloscope (CRO) is operated in a free running sweep mode with a horizontal speed of about 100 cm/s, an observer will see a single horizontal straight line, as expected. If the observer coughs or clears his throat he sees a transient signal. If he sustains a “throat clearing” vibration of about 50–100 Hz, he will observe a steady sinusoidal signal on the CRO. The amplitude of the signal depends on the observer and his vocal intensity, a typical value being 5 mm at a distance of 200 cm. The amplitude increases with distance. Humming does not produce a detectable signal.