Note that in contrast to traditional hydrophone systems, with SoundTraps there is no need to be
concerned with sensitivity in voltage terms. Because SoundTraps integrate the recorder and
hydrophone in a single package, there is a fixed relationship between sound pressure and the
resultant wav file data, thereby simplifying calibration and eliminating the need for voltage
calculations.
Application of the calibration data varies depending on the software used. Descriptions follow for
some of the most commonly used software.
MATLAB
To convert wav data to units of uPa, simply scale by the end-to-end calibration value. Example code:
[y, Fs] = wavread(filename) ; % read wav data from file
cal = 173.3; % value from calibration sheet
cal = power (10, cal / 20); % convert calibration from dB into ratio
y = y * cal; % multiply wav data by calibration to convert to units of uPa
PAMGUARD
PAMGAURD expects calibration data in terms of gain and ADC range. To work around this, specify a
preamplifier gain of the calibration value * -1.0 (eg -176.0) and specify the Peak-Peak voltage range
as 2.0 V.
PAMGuide
PAMGuide provides several convenient calibration schemes. For SoundTrap data select the end-to-
end calibration type and enter a system sensitivity of the calibration value * -1.0 (eg -176.0).
Audacity
Audacity reports SPL in units of dB re full scale. To scale SoundTrap data use the following:
Value in dB re 1 uPa = audacity value + end-to-end calibration – 3dB;
For example, if the end-to-end value from the calibration sheet is 176.0 dB, and audacity reports a
level of -70 dB, the calibrated SPL is 103.0 dB re 1 uPa.
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