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THE POPULAR SCIENCE MONTHLY. 



A simple noise being a sound-wave, has its wave-form or make- 

 mark. The blending of many such would produce a tone in that like- 

 ness ; hence, a musical note is a blending of like noises, and every 

 noise is really the first wave, the key-note of a musical tone. Take the 

 ringing of a door-bell. Here the ear hears not only a musical tone, a 

 sound-blend, in the ring of the bell, but also the noise of the clapper's 

 clang, clang, clang. The vibrations of the bell throw the air into 

 musical waves, shown in Fig. 5, while a huge clang-wave will sweep 



Fig. 5. 



along among the Ww^r-waves every time the clapper strikes. If these 

 clang-waves were to come along fast enough to blend, and at regular 

 intervals, they would produce a tone of their own. The clanging of 

 the clapper would not be a noise, but a deep tone, perhaps making a 

 chord with the ring-tone. But, as it is, the clang-waves come irregular- 

 ly and slowly, and only a noise is the result. The clang-wave is not 

 represented in the figure, but may be easily imagined. From this we 

 see that different sets of air-waves can move along together, and, 

 though they should conglomerate, the ear can single them out. And 

 now we can explain the peculiar character of different sounds, repre- 

 sented by the different forms of waves in Fig. 4. If the string in Fig. 

 1 would really vibrate in a clean sweep as it appears to, it would make 



Fig. 6. 



a smooth wave-form, like A in Fig. 4 ; but, while it vibrates as a whole, 

 in starting the vibration of the string the sudden jerk on it will run 

 along the string in a sort of wabble-wave to its ends and back again, as 

 long as the string vibrates. 



These wabble-waves, in passing each other as they run back and 

 forth on the string in opposite ways, will form stand-still crossing 



