Handbook of High Speed Photography - IET Labs, Inc.

Multiple-flash, stroboscopic photography used to track down the specific sources of
noise in a textile loom for the purpose of noise reduction. Photograph above shows
the setup with Strobotac, camera, end of loom where shuttle flight terminates, and
microphone to pick up noise. Oilier equipment, not shown, includes a dual-beam
cathode-ray oscillograph, a photoelectric cell, two pulse generators, and an oscillator.
The photoelectric cell detects the approach of the shuttle and triggers the oscillograph
sweep and Ihe first pulse generator, which in turn triggers the second pulse generator
after a delay long enough lo allow the shuttle nearly to reach its deceleration point.
The second pulse generator acts as a "gate" lo allow the oscillator to trigger a burst
of about 17 flashes from the Strobotac at a rate of 500 flashes per second. Photographs
are taken in a dark room, with Ihe camera shutter controlled manually.
Photograph below shows shullle with while flag to mark position. At lower left is
a multiple-flash stroboscopic photograph showing Ihe shuttle's while flog as the shullle
decelerates. At lower right is a photograph of Ihe oscillograph screen showing, on Ihe
upper trace, Ihe timing of the light flashes in relation to the noise level delected by Ihe
microphone and shown on Ihe lower trace.
Analysis of these photographs allows a definite correlation to be made between decel
eration and instantaneous noise level, as a result of which the noise-conlrol engineer
can learn where effort lo reduce noise can most effectively be applied. Courtesy of
Mr. Allen L. Cudworth, Liberty Mutual Insurance Company.
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