This application note describes the use of the ADC-212 virtual oscilloscope to measure the speed of sound.
Items used :-
The experiment was setup as shown below with the two crystal microphones placed 1 metre apart.
The balloon was burst approximately 2M away from the foremost Mic. The plot below shows the results clearly.
The lefthand "Blue" trace is from the foremost Mic (Mic1) and the righthand "Red" trace is from the furthest Mic (Mic2).
The waveform from Mic1 between -164uS and 500uS is clearly visible in the trace from Mic2 delayed by 2929uS.
There is a second variation, in the waveform from Mic1, around 1.5mS caused by an echo from one of the walls or ceiling.
From this plot we can measure the time between the two waveforms - 2929uS.
This is over 1 Metre which equates to 341.4M/S.
When calculating the speed of sound through the air we need to take into account the factors which can affect the speed.
The main factors are :-
We can use the table below to find the expected speed :- 344M/S or 2.907mS/M.
The matches very well with the observed results shown above.
L.A.N.Z.O Sweden AB