The background humm, is because of the crappy sound card, it does that with any mic I plug into it.
But it works very good with my portable tape recorder, I was able to hear my self talk just by holding it against the door (it turned the whole door into a mic)
There is no background humm with the tape recorder, so it has to be the computer.
When I used the tape recorder, and then put the transducer on the door, it even picked up some of the birds outside. I used the bedroom door, so it was nowhere near the outside of the house. It seems some meterials pick up sound better then others. Especially wooden doors.
Here is a pic of my piezo setup:
**broken link removed**
Note that the tape I used to hold it to the window is still attached.
I have attached a sound file, this time I recorded it off the tape recorder, in this one, you can see the true recording quality of this transducer. Please note that the noise you are hearing (other then me talking) is the sound of my hand moving, I would have to keep it very still to keep it from making a lot of noise.
Since the file is only 100kb, I put it in a zip file and attached it using the forum.
Don't be fooled, it sounds like its coming from a normal mic, but its from the piezo. It seems doors make much better mics then window panes. lol.