Yes. Please contact me directly (pmm223 at cornell.edu)

You need to know the sensitivity of your hydrophone in volts per pascal, the amplitude of your sine wave calibration signal in volts and the difference in gain between the two recordings. From there it is simple arithmetic. It you don't know all those things, you are probably out of luck.

First, let's get a question of terminology taken care of: to calibrate something, you need to do two separate processes. These are characterization and adjustment. Characterization is the act of finding what a device's response to a known stimulus or signal is. Adjustment is the act of changing the response of the device under test (or DUT). Calibration is the term that refers to the process of characterizing, adjusting, and re-characterizing a DUT so that its response is as close to perfect as you can make it. In your case, I don't imagine that you can change the response of the hydrophone or the recorder, so we'll just call what you want to do characterization, and use the data from the characterization to adjust your data via post-processing in software.

There are two ways to do this for your system: the first is to characterize the hydrophone and recorder separately, while the second is to characterize them together. If you do them separately, then you'll have data on both devices in case they're used with other devices in the future. If you do them together, then you'll have a faster method to get data on the setup you currently have. The choice is yours, and I'll describe the latter method first.

One aside first, though: the limit here is equipment. You'll need a calibrated hydrophone (hereinafter known as the standard hydrophone) that can give you a well-known sensitivity that is relatively flat across its response bandwidth, and you'll also need an underwater sound source, like an underwater speaker, or a speaker that's leaning up against a bucket or tank of water.

The first thing to do is set up your hydrophone (the 96-MIN) and recorder to make your recording. Set up the standard hydrophone so that its output is going into an oscilloscope. The hydrophones should be co-located at a distance of at least 10 cm from your sound source. Send a 1 kHz sine wave into the speaker at a variety of different levels (I usually do 1, 2, 5, 10, 20, 50, 100, 200, and 500 mVrms, and 1, 2, 5, and 10 Vrms). At each level, write down what amplitude the oscilloscope shows from the standard hydrophone. What you have now is a response table for the sound source, where the abscissa is in source voltage, and the ordinate is standard hydrophone voltage. The standard hydrophone will have a sensitivity in either V/µPa or dB re 1V/µPa. You use this number to convert first to µPa, and then to dB re 1 µPa, which will then give you the sound source SPL at each input voltage. When you're done with this process, repeat it for at least three other frequencies across the range of frequencies that you're interested in recording. Take the recording, and bring it into Raven. Once there, you'll only want to use the waveform view. Put your cursor over the portion of the waveform that's at the amplitude that you want, and then take down the minimum and maximum displayed at the bottom of the Raven window. These are the values from the sound file in Least Significant Bits (LSBs). The conversion factor that you need is LSB/µPa. To get this, graph a line with SPL as the abscissa and LSBs as the ordinate for each frequency. You can then use the line fit of your choice to generalize a dynamic response function for each frequency, and possibly one of the form H(A,f) for the entire response surface.

Similarly, if you want to characterize the response of the hydrophone and recorder separately, repeat the process as above, but use the oscilloscope for both the standard hydrophone and the DUT hydrophone, and then use the voltage source as above, but directly connected to the recorder's input. You'll get the same data out from the recorder, but instead of being in LSB/µPa, it will be in LSB/V, and the DUT hydrophone's output will give you V/µPa. Thus, if you multiply the two, you'll get the same LSB/µPa that you had above. These conversion units are all known as sensitivities, and can be used outside of the hydrophone/recorder system if you interface with anything else.

(Don't mind my pedantic insistence on proper terminology, I used to do protocol design for a calibration and metrology company.)

Hi guys, Im on my first research using bioacustics, great info. Thanks

Please see the link at the end. This is a proceeding paper where a portable recorded is calibrated for acoustic measurements. We used an standardized microphone so the complete system calibration was made using a simple acustic calibrator (94 dB@1kH). I do not have experience with hydrophones but perhaps you have an hydrophone calibrator or something similar.

Hope it helps.

http://www.fceia.unr.edu.ar/acustica/biblio/consumer_recorders_for_noise_measurement_INTERNOISE_2010_993.pdf

Ernesto: This paper looks like a good comprehensive overview. My experience with hydrophones makes me think that you'll need multiple amplitudes (since their sensitivities aren't linear), and multiple frequencies (since their frequency responses aren't linear either).

you need the service manual of the recorder. everything stands inside.

i think, you can get it from sony

but be aware that you need test tapes and an audio analyzer to align the recorder.

Hi guys thanks a lot for your contribution. this is my third day on ResearchGate and I am amazed by the rapidity and quality of your replies. This is a really powerful tool for research!

To Mario: you are right, the hydrophone comes with a certificate from HIGH TECH INC. saying that the sensitivity of my hydrophone is -164.1 dB re: 1V/uPa (measured by comparison method with a reference hydrophone.

To Peter: I can feed the pure sine wave in the recorder though the microphone jack but I still don't have clear how can I connect the oscilloscope to the recorder in order to read the voltage. Thanks a lot for your precious and detailed contribution.

Tullio and Mario: I've dealt with the HTI 96-MIN, 94-SSQ, and 90-U, and none of them are any closer than ±5 dB re 1 V/µPa. It's a pretty wide spread.

Tullio: What are you feeding the sine wave signal from? If it's a function generator, you can adjust the voltage there, and count that as your standard. If it's a computer, you'll need to use some sort of splitter and adapter (like http://www.seeedstudio.com/depot/trs35mm-to-bnc-probe-converterdso-nano-compatible-p-561.html ) to measure the output audio on the oscilloscope while sending it to the recorder's input.

Peter: Thanks for your explanation on the hydrophone characterization. I suppose the same method can also be employed for microphone and accelerometer characterization.

I find it almost impossible in the absence of anechoic chamber to obtain the frequency response curve similar to those provided by the microphone manufacturer. I wonder if the method you have outlined is documented anywhere which we could refer to and cite.

I do no thrust any of the suggested calibration methods, apart the latest answer.

I only thrust a Bruel & Kjaer pistonphone (an acoustical calibrator) equipped with the proper airtight adapter (with O-rings) for fitting your hydrophone. All the other calibration methods are, more or less. questionable and unreliable.

I managed to purchase on Ebay my B&K Pistonphone for less than 200 USD, and to build the airtight adapter in my mechanical workshop in less than 1h work...

If the matter is to calibrate the Hydrophone, this is another matter. In Naerum, B&K, they have a... anechoic swimming pool, to calibrate the Hydrophones! But if the matter is to calibrate the recorder, I think that is enough to measure the voltage in input to the recorder, (I.E. a 1V RMS @1000 Hz) and then measure the voltage in output from the recorder, on play. This is the transfer function of the recorder (frequency dependent, so use a spectrum analyser). Too easy? If you know the voltage out from the hydrophone, when there is a underwater sound (of course, re. 1 microPa, not 20 as in air), that is calibration not of the recorder but of the hydrophone, the transducer, microphone, hydrophone, accelerometer or.... so on, outputs a voltage (eventually, conditioned by a conditioning amplifier). Then.. dB=20Log(Vx/V0), where V0 is the reference, taking into account the sensitivity of the hydrophone the recorder and so on. REMEMBER: do not change the knob of the input recording level of the recorder, between calibration ad measure! Best regards!

use sound calibrator for example B&K 4231 (it can generate 94dB and 114dB @ 1KHz) then you can adjust your recorder sensitivity accordingly

Tullio,

You can research on CEM, Spanish Center of Metrology web site: www.cem.es

Teledyne Reson supplies very high quality Hydrophones that are individually calibrated and ship with their own serial number specific calibration plots, this may alleviate a few steps. http://www.teledynemarine.com/hydrophones/hydrophones-reson

you need a calibration tape and a service manual.