hydrophone help required

[kulachi]

hi all,

i am making a hydrophone for research purpose. I have found a very good and low cost method to make it.

**broken link removed**

but still few things arent clear to me . I am using condenser mic or a piezo element from a piezo buzzer. how can i check the frequency response of the piezo buzzer or a tweeter from which piezo element will be taken ????
Also the housing in this example is a plastic film cannister filled with vegetable oil. does the plastic interface to water decrease the data rate of the sound signal received and how can i increase the data rate ???????

Any help would be highly appreciated

Thanx in advance
Regards
Ali Abdur Rehman

 

[klystron]

The transmitter frequency response is a function of the transducer resonance. (The receiver bandwith will be wider)
An impulse response is a good method to measure the frequency reponse.
You can make an impulse with a piston and cylinder. Hit the piston with a hammer.

The speed of sound in the air is around 300 m/s . The speed of sound in water(shallow) is 1200 m/s.

 

[kulachi]

thats the way if i make that hydrophone fist ....
but i want to check the frequency response of the piezo element like this

i have a spectrum analyser and a frequency generator in the lab
can i check the frequency response with these two lab equipment ???
if yess i donnt know the connections of both with piezo element

 

[FvM]

To measure the frequency response of a microphone, you need a speaker and a reference microphone of good quality.

The shown piezo beeper disc is a small band transducer with a strong resonance in the kHz range. I can't imagine that it will be a good microphone, even if immersed in a liquid.

 

[kulachi]

unfortunately i dont have any reference mic :sad:
can i use normal headphone mic ????
also i mentioned about singal generator and osciloscope can i use them to find the frequency response??

 

[klystron]

To determine the frequency response of the PZT sensor you can connect a digital oscilloscope to the terminal of the sensor. Capture the waveform generated by breaking a pencil lead on the sensor. The pencil break is close to a dirac function. The FFT of the measured signal will be the frequency response of the sensor