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Calibration Issues#

I have a hydrophone which is not a SoundTrap which has a given sensitivity in dB re V/1uPa. How do I calibrate this?#

The best method for calibration is to use the ‘signal’ option in ‘Calibrate’.#

This will calibrate the whole hydrophone and recorder system. A known sound level is applied to the hydrophone (using a calibrator) and the resulting signal produced by the recorder saved. This ‘reference’ signal is then loaded into the calibration routine by pressing the ‘Load reference signal’ button and the sound level produced by the calibrator entered.

Alternatively, you can use the ‘Factory values (SoundTrap)’ calibration option.#

This is currently set up for SoundTrap devices. However, the SoundTrap end-to-end calibration value is simply the SPL (dB re 1uPa) value for a maximum possible amplitude of a pure tone in the wav signal (i.e. an amplitude of 1.0). The inverse of this end-to-end calibration is the signal generated by a SPL of 1uPa and is often called the whole system calibration (i.e. from hydrophone to wav file). To get the whole system calibration (which consists of a hydrophone and a recorder) you must add the calibration value for the hydrophone (expressed in dB re 1V/uPa) to the gain for the recorder (i.e. the wav file signal amplitude for 1.0V of input signal amplitude voltage- expressed in dB re 1/V). You take the negative of this whole system calibration number to get the end-to-end calibration value which you can use in dBWav.

Calibration example

If your hydrophone calibration is given as a sensitivity of -210dB re 1V/uPa and the recorder has a gain of 4dB re 1/V then the whole system calibration to use is -210+4 = -206dB re 1/uPa

The end-to-end calibration value to use in dBWav is 206dB re 1uPa.

Note

Recorders often have adjustable gain settings, so the user needs to be careful to ensure that the correct recorder gain is used.

You will need to set up a calibration for each recorder gain setting if you use multiple recorder gains.

Warning

dBWav does not explicitly display the decibel scale reference value in graphs and tables and hence does not need to know this. The reference value is implicit in the calibration value used. Usually, 0dB is defined to be 1uPa, but the user could change this (dBWav can be used for airborne acoustics analysis by assuming 0dB = 20uPa in the calibration).

We would like to use our sensitivity calibrations across the spectrum to calibrate the waveforms. How do we do this?#

Currently dBWav only has a one level calibration for all frequencies. If you need to calibrate across a range of frequencies, you could set up a weighting in the ‘Weightings’ for a specific transducer / target combination using the Tabular Definition option.