Using sound/audio as a potentiometer?

[T.Jackson]

Your best bet would be to forget about sound levels altering resistance and modify the schema to work directly with a DC level that is proportional to db. A cheap, readily available 50 cent mic, plus a 741 (or similar) operational amp a long with a handful of passives is all you really need to do the job. The task of the OP AMP is to amplify the very small AC signal from the mic. You'll also need a sample & hold circuit too. Do a google search on VOX projects. This may help point you in the right direction.

[T.Jackson]

VOX circuit (bit overboard but good) <a href="http://www.rason.org/Projects/basicvox/basicvox.htm" target="_blank">Click Here!</a>

[Ioannis]

From the circuit you should throw away Q1. Then put in the place of R9 a 5.1V zener to protect the PIC adc input. The circuit functions as simple rectifier, so the audio level as converted to dc.

The op-amps may need high power supply (of 12 or more volts). Another choice might be LMC662.

Ioannis