Hi,
I am starting to look into a project which requires a very sensitive mircophone/vibration sensor and wondering what folks might recommend?
The aim is to pick up, stethoscope style, very quiet noises/vibrations within solid bodies without interferance from airbourne sound - for example, to listen to termites eating a log.... 
Would be great to get thoughts.
Modified turntable stylus pickup?
Nice idea AWOL - wonder what level of output these provide. I guess the stages would be to put the signal through an amplifier and then find an arduino shield to turn this output into sound?
Electret microphones are very sensitive. I've even seen them working as a stethoscope in an old electronic blood pressure meter.
The thing is, I guess,how to isolate them from external noise. Sounds like noise cancellation (active or passive) is required.
Sounds like you want a contact microphone.
Here's one made from a Radio Shack piezo transducer:
http://home.earthlink.net/~erinys/contactmic.html
Joe
Thanks folks, I will try some of these - may I ask what the best way would be to output the sensor output as audio?
I've built an analog stethoscope years ago. What worked very well was a small speaker attached to the skin. You just have to be careful not moving it.
Still have some schematics around? The analog sound could be sampled by the Arduino somewhere ...
You can get / I've got free samples:
The socket is $3.
With this:
I can literally detect a pin dropping.
I've modified the circuit a little.
Nice picture of the champagne bottle !
Might be a killer app for marriage-photographers etc!
robtillaart:
@cyranoStill have some schematics around?
Sorry. This was in the pre-digital world 
The analog sound could be sampled by the Arduino somewhere ...
The problem isn't getting enough gain. It's in differentiating between the signal you want and the noise from the environment. I actually had to add some weight to the speaker, simply by gluing on some washers. Then, this speaker/mic was attached to human skin, not a hollow tree.