Demo of the physics

A project log for sound-based weather station

Converts weather into microphone-vibrations that DSP on a small computer can resolve into weather data

Dave MerrettDave Merrett 04/06/2016 at 09:590 Comments

Ok, So I mocked up some stuff to demo the physics involved. The picture here shows a synthetic wind (fan) blowing onto single cavity ( aka pop-top bottle) , which exhibits directional amplitude response to wind, and bulk-amplitude response to wind-speed.

So I installed an electret microphone into the bottle , and connected it to the mic-input of a sound card . The sound, when heard, as expected, is mostly 'brown' noise generated by the wind hitting the lip of the open top. Inside the bottle, various tones ( typically harmonics of the resonant frequency ) dominate the spectrum beyond the low frequency band of noise. This was discovered using sdr-sharp, to display the spectrum, which was captured in screen shots below.

As I rotated the bottle, the amplitudes ( absolute and relative) of the various frequencies changed accordingly.

Here's the whole setup on my dining table..