simple volume meter? how to?

Hy,

I'm trying the following. I wanna measure the sound level in a room, and then light up a led in a certain intensity. so how can I easily measure the loudness.

It's not important how accurate it is, I just need to have a signal to the arduino.

What is the easiest way to do it?

thanks for the help!

edit: maybe this one: http://shop.lego.com/Product/?p=9845

Or this one: http://www.sparkfun.com/commerce/product_info.php?products_id=8669

http://www.bowdenshobbycircuits.info/page11.htm#vumeter.gif

if you want to go old school that is...

Sometimes, going old-school is the best thing to do; that comparator circuit (providing it is accurate; at first glance it looks ok to me) probably costs less than $5.00 to make and would likely give exactly what the OP needs; it depends on if he is wanting to learn something new, or get a job done, I suppose.