Page:Popular Science Monthly Volume 89.djvu/80

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How the Voice Typewriter Works


















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���This is the machine itsed to evolve the natural alphabet. The man at the left is whispering into an acoiistieon or loud- speaking transmitter, which is attached to a heavyweight, in turn suspended by springs. The inertia of the weight and the resiliency of its spring supports, prevent exterior vibrations of arty kind from jarring the extremely sensitive transmitter. Connected with its circuit is a siring galvanometer. The whole ar- rangement is so sensitive that faint whispers readily cause the "siring" to vibrate. Light from t!:e arc light throws a shadow of this vibrating string on to the camera at right. A revolving drum carries a strip of photo- graphic film and rnakes a permanent record of the vibra- tions. Sample records are given at left, together with an explana- tion helo;i' of what those par- ticular curves signify.

��These strange curves are records of the whispered and spoken vowel " U"

��The strange curves sho-wn aitove are records obtained from the ap- paratus. Upper Curve: Man's voice pronouncing the letter " U" bringing out in striking fashion the fact that any underlyiyig curve is obscured by extra humps due to the peculiar nature of the particular speaker's voice. Middle Curve: Woman's voice pronouncing the same tetter " U ." Note differences from same letter pronounced by man's voice. Lowermost Curve is ob- tained when the letter " U" is whispered. Whispering is the most elemental way one can transmit speech, since it does not require use of the vocal cords. Contrast this curve with the two preceding. Note that instead of a series of repealing diagrams

��peculiar to a particular speaker's voice, a definite undulation or wave-shape now appears. In the two upper curves this under- lying wave-shape was blotted out by extra curves or humps knmvn as "higher harmonics" which arose from the use of vocal cords and were different for different men's and women's voices. This underlying wave-shape 7uas none the less present in the two upper curves, because a sound shaped in this precise manner is neces- sary before the twain recognizes the letter " U" as such, Mr, Flowers' feat consists in recog- nizing this principle, and in demonstrating it. He whispers the whole alphabet into the transmitter of the apparatus shown altove, and secures ac-

��curate pliotographs of the undula- tions, or "letter patterns" result- ing, A complete set of these is shown on Page 68. Mr, Floivers found that it makes no difference who does the whisper- ing; the same wave form for the same letter always results. Scien- tists recognize this as an immense step in advance, because hereto- fore men attempting to get at the real nature of speech have always been frustrated because the higher harmonics blurred out the true wave present. They could not deal with whispered speech because no apparatus sensitive enough to record whis- pered speech existed, and the curves they obtained with spoken speech varied hopelessly with each different speaker's voice.


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