The French scientist Pierre Gassendi
(1592-1655) made the first known attempt to
measure the speed of sound in air. Gassendi measured the delay between
seeing the flash from a distant gun and hearing the explosion. He
made the correct assumption that the speed of light is effectively infinite
and obtained a value of about 480 m/s, significantly higher than the modern
value of 330 m/s. Later workers used the same technique but obtained
better values than Gassendi.
You will measure the speed of sound in essentially the same way as Gassendi, although you will be aided by $10 stopwatches that are considerably more accurate than anything Gassendi could have used. Instead of a gun, we will use a camera flash wired to a hammer and a metal plate. When the hammer strikes the plate (creating a racket), the head of the hammer and the plate complete a circuit that fires the flash. You will time the delay of the sound with respect to the flash for several distances from the plate, and use your results to calculate the speed of sound in air. Along the way you will learn about random and systematic errors in data and how to account for them.
Updated 8/24/00 by Peter N. Saeta .