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Re: Fourier transforms & Spped of sound



Hi,
In this experiment we use a 2 meter long, 3 cm
diameter pipe with both ends open. A student
blows across one end, basically producing white
noise ( or maybe "blue" noise because the
amplitudes at low frequencies are small) At the
other end is a microphone and audio amplifier that
is digitized by an Analog to Digital Converter
card in a PC. Students (College juniors and
Seniors) need to pick the sampling rate and length
of sample that produces good results.

After the sampling the data is run through a
small program that does an FFT taken from the
book "Numerical Recipes". I hav not been in that
code for a while but the amplitudes are all
positive. So probably the absolute value are
displayed.

Thansk
Roger Haar


************************************

Ludwik Kowalski wrote:

SNIP

I do not know how the FFT
analysis is performed by Roger (please share the details) but
I suspect that his hardware captures a certain finite number of
cycles to be processed. That is why the output is never a
single value of w.

SNIP