Quick Question

I recently built a circuit using a type of speaker that I know nothing about. So I was wondering what kind of speaker it is.

The speaker is really flat like a centimetre or 2 in height. Most of the time they are made of plastic and they have a hole in the center which you can see some kind of metal sheet inside. I usually find them in musical Christmas cards and in kids toys.

I think its similar to a crystal microphone but I'm not sure. Any ideas? thanks.

well, it would be best to place a picture of it.....
i think it is a piezo speaker or a buzzer.
how does it respond to low frequencies?

**broken link removed**

i'm not sure about low frequencies but i think its a good at high ones. The speaker in my circuit was used as a sound sensor. and i noticed that when i used low battery power the speaker would buzz. so my guess is that with full power the speaker is making tones i can't here.

Anyone? Sorry I don't know much about speakers.

Yes it's a piezo-buzzer (as Bogdanfirst wrote) in tuned plastic case.