Page:Popular Science Monthly Volume 45.djvu/89

Rh periodic; a periodic motion being one that repeats itself." And, again, quoting from Tyndall: "To produce a musical tone we must have a body which vibrates with the unerring regularity of a pendulum, but which can impart much sharper and quicker shocks to the air. The pulses, on the contrary, which produce noise are of irregular strength and recurrence." These illustrations will no doubt afford a fairly clear understanding of the creation and composition of sound, and we will now consider some of its effects.

One peculiar phase in sound effects is the sympathetic response of objects in the vicinity of a sound or note, such as the responding vibrations of a violin string when a note on the piano is struck with which it is in harmony.

This peculiar effect, however, is by no means confined to musical instruments, for should there be any object in a room which by accident happens to be so placed as to be in unison or tune ~with some note of a piano, that object will respond by taking up the vibrations of the note sounded. This responding note being often accompanied by a disagreeable jarring sound (due to the article touching some object while vibrating), interferes with the harmony and is often the cause of much annoyance to ladies and others who may be playing the piano; besides, these foreign sounds are so deceitful as to their location that usually they seem to come from the piano itself, and it is generally very difficult to convince a lady that they are anywhere else, and in the ladies' opinion a piano tuner must be sent for as soon as possible. An instance or two which happened in my experience will illustrate this.

The first case happened in my own home a few years ago. My wife and myself were in the parlor, she playing the piano. Presently she stopped and impatiently said, "There, this piano is not right yet, and that tuner has been here three times, and this is the note he fussed over so long" (pounding on the same), "and it's just as bad as ever." The fact was, the last time the tuner called he went away very mad, stating that he never had had such a case in all his experience. Knowing all this, the remark of my wife set me to thinking, and I asked her to pound awhile on that bad key. Upon listening carefully about the piano the jangling noise did really seem to come directly from it; but determined not to be deceived, I started on a tour of investigation, first satisfying myself that there were no loose objects upon the piano itself. I began to look about the room among bric-à-brac, mantelpiece ornaments, etc., now and then receiving such encouraging remarks from the performer as "There is no use looking away over there for that noise, it's right here in the piano; don't you hear it?" But I said, "Never mind, keep on pounding."