PECULIAR SOUND EFFECTS. 77 



f ectly periodic ; a periodic motion being one that repeats itself/' 

 And, again, quoting from Tyiidall : " 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 illustra- 

 tions will no doubt afford a fairly clear understanding of the crea- 

 tion 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 respond- 

 ing 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 mu- 

 sical 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 diffi- 

 cult 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 illus- 

 trate 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. Pres- 

 ently 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 satis- 

 fying myself that there were no loose objects upon the piano 

 itself. I began to look about the room among bric-a-brac, man- 

 telpiece 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." 



