# B Piezoelectric transducer

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1. Jul 30, 2016

### Sveral

2. Jul 31, 2016

A google of the topic shows that piezoelectric transducers can make useful microphones, but the frequency response is not as good as some other forms so that they generally are not used in high quality sound systems.

3. Aug 1, 2016

### Sveral

Would the transducer in the link be a good idea for a microphone? Any ideas, what I could connect to it, so it can output ultrasound?

4. Aug 2, 2016

### Hunter235711

I've played around with taking piezoelectric transducers out of musical greeting cards. They are much better at picking up sounds through solids (like a stethoscope) than they are at picking up sounds transmitted through the air.

To hear the signal the piezoelectric disc is outputting you will need an audio preamp. Check out this one: http://interface.khm.de/index.php/lab-log/piezo-disk-preamplifier/

-Hunter

5. Aug 2, 2016

### nasu

It's not clear from your posts what you actually want to do.
A microphone does not output sound but convert sound into electrical signals. So the sound is the input for the microphone and not the output.

Fortunately, piezoelectric transducers can be used as both receivers of sound and emitters of sound. In many cases the same transducer can be used for both.
However, the tranducers are usually designed for a specific frequency range and they may have very poor performance outside this range.
The one in the link is for 1.68 MHz, so for low frequency ultrasound.
It may work in the audio range too, with reduced efficiency.

So, you want to produce sound or detect sound from other sources?

6. Aug 2, 2016

### litup

What frequency range are you interested in? They are inherently bidirectional, that is you put in AC you get sound, you put in sound you get AC out of it.

But the kind of material, thickness and so forth gives the resonant frequency which in the example you showed was over 1 megahertz, not useful for human style audio or even Dolphin audio (200 kilohertz) so you have to define what frequency range you are interested in.

BTW with a buddy in Jerusalem, we had a few weeks to experiment and found the sono-lert type audio piezo's could be cut with sissors where one side disintegrated and the other cut cleanly so turned it around and cut again and was left with a strip say 5 millimeters by 25 mm or so, useful to attach to a mandolin bridge.

It sounded great BTW, in that use.

7. Aug 2, 2016

### Sveral

I want to produce sound. I wanted it to output audio signals at ultrasound frequency, but in a pulsed manner, was informed, that the human ear can perceive ultrasound, when its pulsed instead of continuous.

8. Aug 2, 2016

### Sveral

Im interested in roughly around 50 kHz in a pulsed manner.

9. Aug 2, 2016

### nasu

You can excite the transducer any way you want. The pulsed waves are used in both industrial and medical applications of the ultrasound.
However, I see two problems. Your transducer is tuned for a frequency much higher than 50 kHz so its output may be quite low, if any.
And besides, these transducers are impedance matched to water (I understand it is for ultrasound cleaners). So its output in air, even at its resonant frequency, will be very low.

Do you have any reference for this claim about perception of pulsed ultrasound?

10. Aug 4, 2016

### Sveral

So a better option would be to transmit the sound directly through the body, skipping air as a whole?
The only reference I have for this claim is an experiment, that was conducted during the high school years of another forum member on here...

11. Aug 4, 2016

### nasu

You can couple to the body by some gel or even water between the transducer and skin. This is routinely done in medical ultrasound.
But to get it to the ear may be more difficult. Why not use a better transducer, maybe air coupled and designed for this very low frequency range?