[chbot] Simple Sound Level Meter Circuit

[Spencer Travers]

Hi all,

I am working on a classroom environment monitor project with a group of
intermediate students (11-13 year olds). One component of this project is a
very basic sound level meter connected to an Arduino. We have tried a
Freetronics microphone interface board (schematics at
http://www.freetronics.com/products/microphone-sound-input-module<http://www.freetronics.com/products/microphone-sound-input-module#.Ug9RbZJ9t-0>)
with poor results. The module seems to be very noisy and the output appears
to oscillate.

We are essentially after a circuit to sample the background noise level and
provide a 0-5 V output for the Arduino ADC to read. We are not too
concerned about accuracy as the output will be a traffic light
red/orange/green display. If the Freetronics module had worked as
advertised it would have been ideal.

Can anyone out there suggest a modification to the board we have or an
alternative circuit?

Spencer
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