MUSIC MEASURES SPEED

Evening Star, Issue 19443, 29 December 1926, Page 8

MUSIC MEASURES SPEED

NEW USE BY THE MIDDLE U. How would you go about measuring the number of revolutions per minute of some small piece of machinery that was probably turning over at the rate ol .50,0011 times a. minute—over BUO times a second? The task would seem almost impossible, yet it has been accomplished with a. considerable degree of accuracy (says ‘ Popular Mechanics’). Tho latest method is to measure the high speed by comparing it with notes of the musical scale. A tiny dynamo is built on tho spindle, which is then set in revolution at whatever speed is to be measured. The dvnnmo generates an alternating current, which is led through wires to headphones. Each complex cycle of the alternating current draws the headphone diaphragm, in toward the magnets once and releases it once—a complete vibration. Thus the number of vibrations per minute will correpond to the revolutions made by the spindle. Tho musical note known ns middle C is produced by 261 vibrations a second, so that when the operator hears the middle G coming in through tho earphones ho knows that the spindle is ( making about 261 revolutions a second. In. the same way other speeds may be compared with other notes.