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.
55/370 page 35
![it is important to use a source of tone production which will emit a tone of constant pitch. The notes of the minute whistle (Galton’s whistle), which is usually employed, vary considerably in pitch according to the pressure of the wind blowing it. The upper limit is also influenced very sensibly by the intensity of the tone, a feeble tone being inaudible while a louder one of the same pitch may yet be heard. The lower limit of hearing is a tone of from fifteen to twenty vibrations per second. The upper limit is a tone of about 22,000 vibrations per second. From youth onwards the range narrows at both ends, becoming reduced in old age by about an octave. By no means the whole of this available range of about eleven octaves is employed in music. The notes of a grand pianoforte extend over a distance of less than eight octaves, from A2 (26*6 vibrations) to cy (4096 vibrations); the organ has a range of nine octaves from C2 to cvi. [ The Smallest Perceptible Difference of Pitch.—Some of the conditions which affect our ability to discriminate between small differences will be alluded to hereafter (Chap. XIX.). The smallest interval that we can detect between two succes¬ sive tones is known as the differential threshold, or as the threshold of discrimination, for successive tones (exp. 120). Over the middle part of the tone range it is fairly constant. Practised observers are just able to detect differences in the case of the following pairs of tones :—64, 64*15 ; 128, 128*16 ; 256, 256*23; 512, 512*25; 1024, 1024*22; 2048, 2048*36. Judgment of difference, however, is easier than one of direction of difference. The pairs of tones just named are too nearly alike for the observer to decide which is the higher or the lower, even though he may be able to detect a difference between them. Towards the upper and lower limits of the range of audible pitch, discrimination becomes less delicate. Indeed, near these limits, the threshold of discrimination becomes astonishingly high.] Beats and Intertones.—If two tones of nearly identical pitch are simultaneously sounded, ‘ beats’ occur, the frequency of which depends on the vibration difference of the tones 3—2](https://iiif.wellcomecollection.org/image/b3135984x_0001_0055.jp2/full/800%2C/0/default.jpg)
