Sound from a Piezo Transducer

[MagnumForce]

This is a audio clip recorded from a Piezo Transducer. Surprisingly, I didn't need any special amplification.

**broken link removed**
(note, don't right click save as, since this is not a direct link)
I used rapidshare to host the file.


I have a portable tape recorder that has a mic jack, and it also seems to work very good with them.

I taped the transducer onto my bedroom window, and recorded the resulting sound. I was able to capture some thunder near the end of the audio clip. You will have to listion carfully for it. (it was raining at the time)

Please note, I recorded it with a crappy sound card, so once I get a better computer, the sound will be better.

This next audio clip was recorded this morning (CDT) and was able to record the birds chirping outside!

**broken link removed**

Most of the background noise you are hearing is the sound of cars going by, since I live next to a highway.

It seems that it records at the frequency of the window pane itself, since when cars go by, the resulting noise is similar to the natural frequency of the windows pane.

 

[Dr.EM]

Yeah, its suprisingly good sound. I can hear the quite prominent 4k area, but the noise level is quite acceptable, I thought it might be higher with that sort of output impedance.

On another point, if I din't know better, i'd say that rapidshare place wanted me to buy a premium account :shock: :lol:

 

[chemelec]

I don't find that very surprising.

Many Years Ago, there were Crystal Microphones.
Which in reality are Piezo's.
They also made old record player cartridges the same way.
All are Very High Outputs and good Sensitivity.

The Typical signal output is about 1 volt.

On my website, I have some Crystal Lapel Microphones for sale.
Yelling into them gives an output of about 1.4 volts.
And REALLY SENSITIVE to soft sounds.

The Frequency response of these is Poor at Low Frequencies.

 

[audioguru]

I listened to the 1st recording and heard only a loud hummmmm and some backgound noise. Wasn't a shielded cable used?
The diaphragm of a microphone isn't supposed to be taped to a window pane, it is supposed to pickup fast variations in air pressure, called sound.
A piezo transducer makes a lousy microphone, just about as lousy as it performs as a playback transducer. A crappy whistle. A beeper?

Why not use an electret microphone? They have excellent sound pickup and cost only about a dollar. A preamp for them is easy to make if needed.

 

[Dr.EM]

Yes, for doing actual recordings, electrets are very good. I made my pair of phantom powered balanced mics from them, and they are quite useful. But I think Magnum is just experimenting here, and has got a result better than I would have thought.

 

[MagnumForce]

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.