PSN-L Email List Message

Subject: Speed of Sound
From: Geoff gmvoeth@...........
Date: Sun, 7 Apr 2013 13:22:01 +0000

Hello PSN,

I know this is not about EQ
But Id just like to tell you guys
how I measured the speed of sound in AIR
at GVA.

I set up two Identical microphones separated by
some distance like 49 inches.

I set up a stereo recording simultaneously
recording both channels.

I banged two hammers together about ten times
a couple feet away from the lead microphone.

I was able to get the same results by
comparing the arrival times of
the two signals via wave file using Audacity.

I used 48000 samples per second 16 bit stereo.

The results were consistent at 342.9 Meters per second at 85DegF

I have a formula which contains a magic number
to find the velocity at whatever temp
but not sure its right.

VS = SQR(388.767(273 + tAmbAir)) Meters per second

Is this the right way to go to tell the VS
at whatever temperature given this location
stays the same ?

I could imagine looking at rock this way to
see if the VS changes in rock near a
fault zone. Are they doing this
to try and forecast EQs ?

It seems to me if you could somehow
measure constantly the physical
properties of rock near or at
a fault zone you might get an idea
the rock is about to fail ?


It is by the Entropy that I set my mind in motion.
Entropy is the seeking of equilibrium.
It is by the Entropy that I set my mind in motion.


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