Neil's News

Range Finder

31 December 2012

A surplus satellite dish unexpectedly entered my possession. Let's measure distances using the speed of sound. I secured my phone's microphone to the focal point.

Next, I pointed the dish at an apartment building at the other end of the block. I am not fond of this particular apartment building because it blocks my view of the Bay. So acquiring exact targeting information will be useful for future experiments.

Clapping my hands once produced a recording (WAV) which forms the wave pattern below. A small but clear echo shows up exactly 0.258 seconds after the clap.

Dividing by two (outward journey and return journey) and multiplying by the speed of sound at sea level gives a distance of 43.9 meters. Measuring the same distance on Google Earth gives a distance of 43.1 meters.

Only a 2% disagreement between two wildly different methods of measuring distance. Not bad.

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