LOW resonance PIEZO Electric drivers ?(do i have to make one?)

[frd]

I have been up to make an impedance tube to measure acoustic Z and calculate absorption coefficient of materials . and having a sound generator(speaker driver) in it usually gives you near 60 hz response so your data will be charted starting 60hz and above.

My goal is to measure from 20hz to 4khz . and its hard to stick a large box in one side of tube to get low response if possible .

Anyhow I saw somewhere that they have used PIEZOELECTRIC as sound generator so they measure from 20hz.

Question is where to find a piezo that resonances below 20hz ?

or how to make one if I have to ...?

Thanks

 

[K^2]

The reason people usually chart above 60Hz, as I understand it, is interference from the mains. Piezoelectric generators are good for extremely high frequencies. I'm not aware of any benefit at low frequencies.

 

[frd]

how are you sure i have a pdf of set up using piezo for extremely low resonances ...

 

[berkeman]

how are you sure i have a pdf of set up using piezo for extremely low resonances ...

Where did you see a PDF file mentioned in his response?

 

[berkeman]

I have been up to make an impedance tube to measure acoustic Z and calculate absorption coefficient of materials . and having a sound generator(speaker driver) in it usually gives you near 60 hz response so your data will be charted starting 60hz and above.

My goal is to measure from 20hz to 4khz . and its hard to stick a large box in one side of tube to get low response if possible .

Anyhow I saw somewhere that they have used PIEZOELECTRIC as sound generator so they measure from 20hz.

Question is where to find a piezo that resonances below 20hz ?

or how to make one if I have to ...?

Thanks

If you want to generat good-quality sound, it's hard to beat the modern speakers with multiple elements and crossovers. And for measuring the acoustic attenuation (I'm not sure about the impedance you mention though), you can use a microphone before the material as the "Reference", and a microphone after the materal for the "Test" signal, much like you have on the Gain-Phase side of an Impedance meter like the HP 4194.

 

[frd]

here is the link :
http://intellagence.eu.com/acoustics2008/acoustics2008/cd1/data/articles/003579.pdf

i know how to run an impedance test but HOW A PIEZO can generate a 20hz tone ?

 

[frd]

Where did you see a PDF file mentioned in his response?

I posted the pdf ...