> what makes a street light noise unique?
Street lights for some reason have a very throaty low pitch to their
sound.
Although the frequency is fixed by the line voltage, the harmonic content
makes the lights at least here have a very distinctive sound. In addition,
most but not all of these vapor type lights will start to cycle on and off on
about a 1 miunte schedule as they begin to fail. The noise is generated
mostly during the lamp firing process. As the light warms the noise will
diminish in amplitude and usually just as the lamp gets pretty quiet it will
switch itself off and after cooling for a bit it will fire again starting the
noise all over again. Some bad lamps stay on all the time with their low
pitched noise. Most cycling lights or non functioning lights are very easy
to spot at night. Usually an AM BC radio will easily pick up the noise from
a bad light.
Lee K7TJR
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