254 galton.org
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Appendix
The largest whistles suitable for experiments on the human ear, have an inner tube of
about 0.16 inches in diameter, which is equal to 40 units of the scale. Consequently in
these instruments the theory of closed pipes ceases to be trustworthy when the depth of the
whistle is less than about 60 units. In short, we cannot be sure of sounding with them a
higher note than one of 14,000 vibrations to the second, unless we use tubes of still
smaller bore. In some of my experiments I was driven to use very fine tubes indeed, not
wider than those little glass tubes that hold the smallest leads for Mordan’s pencils. I have
tried without much success to produce a note that should be both shrill and powerful, and
correspond to a battery of small whistles, by flattering a piece of brass tube, and passing
another sheet of brass up it, and thus forming a whistle the whole width of the sheet, but of
very small diameter from front to back. It made a powerful note, but not a very pure one. I
also constructed an annular whistle by means of three cylinders, one sliding within the
other two, and graduated as before.
When the limits of audibility are approached, the sound becomes much fainter, and
when that limit is reached, the sound usually gives place to a peculiar sensation, which is
not sound but more like dizziness, and which some persons experience to a high degree.
Young people hear shriller sounds than older people, and I am told there is a proverb in
Dorsetshire, that no agricultural labourer who is more than forty years old, can hear a bat
squeak. The power of hearing shrill notes has nothing to do with sharpness of hearing, any
more than a wide range of the key-board of a piano has to do with the sound of the
individual strings. We all have our limits, and that limit may be quickly found by these
whistles in every case. The facility of hearing shrill sounds depends in some degree on the
position of the whistle, for it is highest when it is held exactly opposite the opening of the
ear. Any roughness of the lining of the auditory canal appears to have a marked effect in
checking the transmission of rapid vibrations when they strike the ear obliquely. I myself
feel this in a marked degree, and I have long noted the fact in respect to the buzz a
mosquito. I do not hear the mosquito much as it flies about, but when it passes close by
my ear I hear a “ping,” the suddenness of which is very striking. Mr. Dalby, the aurist, to
whom I gave one of these instruments, tells me he uses it for diagnoses. When the power
of hearing high notes is wholly lost, the loss is commonly owing to failure in the nerves,
but when very deaf people are still able to hear high notes if they are sounded with force,
the nerves are usually all right, and the fault lies in the lining of the auditory canal.
