Can a Piezoelectric Transducer Double as a Microphone?

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Discussion Overview

The discussion revolves around the potential use of piezoelectric transducers as microphones, specifically whether they can output sound when connected to a user. Participants explore the feasibility of using a specific transducer model for audio applications, including ultrasound frequencies, and the characteristics of piezoelectric transducers in sound detection and emission.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants note that piezoelectric transducers can function as microphones, but their frequency response may not match that of higher-quality microphones.
  • One participant shares personal experience with piezoelectric transducers from musical greeting cards, suggesting they perform better in solid mediums than in air.
  • Another participant emphasizes that piezoelectric transducers can act as both sound receivers and emitters, but their effectiveness is often limited to specific frequency ranges.
  • Concerns are raised about the transducer's tuning for a frequency of 1.68 MHz, which may not be suitable for audio applications, particularly at lower frequencies like 50 kHz.
  • Some participants discuss the possibility of using pulsed ultrasound and its perception by humans, with one participant seeking references for this claim.
  • There is a suggestion to use coupling methods, such as gel or water, to improve sound transmission to the body, although challenges remain in getting sound to the ear effectively.
  • One participant proposes the idea of using a different transducer designed for lower frequencies instead of the one linked in the original post.

Areas of Agreement / Disagreement

Participants express differing views on the effectiveness of the specific piezoelectric transducer for audio applications, with no consensus on its suitability for the desired frequency range or method of sound transmission.

Contextual Notes

Participants highlight limitations related to the frequency tuning of the transducer, its impedance matching to water, and the challenges of sound transmission through air versus solid mediums.

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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.
 
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Charles Link said:
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.
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?
 
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
 
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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?
 
Sveral said:
Hello,
I wanted to know, if a piezoelectric transducer can be used similarly to a microphone to output sound, when connected to the user?
Here`s an example:
http://www.topqualitytools.co.uk/at...UH4lAyheqgLOQGEeq2dm9l1Fi69zGYIMpKRoCuNnw_wcB
Thanks in advance.
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.
 
nasu said:
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?
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 it`s pulsed instead of continuous.
 
litup said:
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.
I`m interested in roughly around 50 kHz in a pulsed manner.
 
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
nasu said:
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?
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
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?
 

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