Volume 1
A text-book of experimental psychology : with laboratory exercises / by Charles S. Myers.
- Charles Samuel Myers
- Date:
- 1911
Licence: Public Domain Mark
Credit: A text-book of experimental psychology : with laboratory exercises / by Charles S. Myers. Source: Wellcome Collection.
58/370 page 38
![at length produced, first the higher, then the lower, of the two primary tones emerging and becoming distinguishable as the interval is increased. Careful attention shows that it is always the intertone which carries the beats. It is of softer character than the primary tones, and is localised within the ear. When in the above example the mistuned prime reaches 300 vibrations, the intertone is almost inaudible (exp. 31). [Sometimes the beating tone may appear to vary, not only in loudness, but in pitch. This is probably due to the promi¬ nence of overtones during the periods of relative silence, and is thus an example of the confusion of change of timbre with change of pitch (page 29). Beats may be heard when the two tones are separately conducted, one to one ear, the other to the other. Careful experiments have been made upon these so-called ‘ binaural * beats. Two electrically driven tuning-forks were used as the source of sound. They were placed one in each of two rooms situated on either side of a central room, in which the observer sat. The tones were led to his ear by means of sound-tight tubes, and were thus completely isolated from one another. The audibility of binaural beats was held to prove that our experience of beats is of central origin, due to the stimulation of the auditory centres by impulses travelling up the auditory nerves. This view meets with very little sympathy at the present day. All recent evidence goes to show that when two tones of nearly identical pitch are led to the two ears separately, each tone passes by bone con¬ duction to the opposite ear, where by interference with the other tone it gives rise to beats. Auscultation of the skull roof by means of a specially constructed microphone has definitely proved that conduction occurs in this way. There can be little doubt that uniaural and binaural beats have the same (peripheral) origin. Beats may be heard when the primary tones, led to separate ears, are so faint that each when sounding alone is inaudible. We shall subsequently see (page 50) that conduc¬ tion from ear to ear is a possible explanation of the audibility of binaural beats from such tones of subliminal intensity.]](https://iiif.wellcomecollection.org/image/b3135984x_0001_0058.jp2/full/800%2C/0/default.jpg)
