. Scientific news for general readers; a popular illustrated weekly journal of science . cy of vibrationdetermines pitch. The shape of the waves determinescharacter, quality, or timbre of the sound. Sounds which aredevoid of definite rate of vibration may be classed as noises,while sounds which have a definite vibration-rate may beclassed as musical,this definition being ofcourse a scientific,notan artistic one. If two sources of sound act simultaneouslyupon any medium, the resultant sound is simply that due tothe superposition of the two sets of waves. It may be pos-sible to pick out both sou
. Scientific news for general readers; a popular illustrated weekly journal of science . cy of vibrationdetermines pitch. The shape of the waves determinescharacter, quality, or timbre of the sound. Sounds which aredevoid of definite rate of vibration may be classed as noises,while sounds which have a definite vibration-rate may beclassed as musical,this definition being ofcourse a scientific,notan artistic one. If two sources of sound act simultaneouslyupon any medium, the resultant sound is simply that due tothe superposition of the two sets of waves. It may be pos-sible to pick out both sounds, one may predominate, and theother only affect its timbre or character, or they may be soblended as to produce the impression of one sound subject is a tempting one, but must not lead us astrayfrom that which we are considering. Enough has been saidto show that all sounds are simply due to successive wavesof high and low pressure in the medium of their propaga-tion. The succession of waves may be regular or irregular,the waves may be rough or smooth in outline, and every. Fig. I.—Illustrating Sound Waves. difference in either character produces a difference in thesound. It is further to be noted that difference in loudnessis due simply to difference of amplitude of the waves, or inother words to the amount of the differences in the pres-sures at the crest and in the trough of the wave. From this it may be easily seen that to produce any soundot a given character and pitch, it is only necessary to givethe medium of propagation a succession of impulses at someparticular rate, and in some particular order, as regards theirrelative amount. If the medium is air, or any other fluid,this can be done by causing some flat surface to vibrate inthe medium in a manner, as to frequency and other points,corresponding to the sound vibrations required. It will alsobe obvious that any flat surface exposed to air vibrations,and free to move in any way, may be set into vibrationsco
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