59.1 " " 25,000
53.8 " " 30,000
50.1 " " 35,000
47.5 " " 40,000
These rods need to be suspended upon loops of silk, and they are struck
with a piece of steel so short as to be wholly beyond the ability of any
ear to hear its ring. Nothing but a short thud is to be heard from it
when it strikes, while from the others comes a distinct ringing sound.
In experimenting with such a set of steel rods I have not found any one
yet who could hear as many as 25,000 per second, my own limit being
about 21,000. But it has been experimentally found that children and
youth have a perceptive power for high sounds considerably above adults.
Dr. Clarence Blake of Boston reports a case in his aural practice, of a
woman whose hearing had been gradually diminishing for some years until
she could not hear at all with one ear, and the ticking of a watch could
only be heard with the other when the watch was held against the ear.
After treatment it was discovered that the sensibility to high sounds
was very great, and that she could hear the steel rod having a tone of
40,000 vibrations.
Last year Mr. F. Galton, F.R.S., exhibited before the Science Conference
an instrument in the shape of a very small whistle, which he had devised
for producing a very high sound. The whistle had a diameter less than
the one twenty-fifth of an inch. The length could be varied by moving a
plug at the end of the whistle. It was easy to make a sound upon such an
instrument that was altogether out of hearing-range of any person. Mr.
Galton tried some very interesting experiments upon animals, by using
these whistles. He went through the Zooelogical Gardens, and produced
such high sounds near the ears of all the animals. Some of them would
prick up their ears, showing that they heard the sound; while others
apparently could not hear it. He declares that among all the animals the
cat was found to hear the sharpest sound. Small dogs can also hear very
shrill notes, while larger ones can not. Cattle were found to hear
higher sounds than horses. The squeak of bats and of mice cannot be
heard by many persons who can hear ordinary sounds as well as any;
sharpness of hearing having nothing to do with the limits of hearing.