signal level recorded. The calibration data is provided as an end-to-end value. This represents the
rms voltage that will result in a normalised (±1.0) wav file with a full scale signal ie 2.0 units peak-
peak.
A typical value is -1.8 dB re 1 V.
Hydrophone Calibration
Each SoundTrap hydrophone is factory calibrated. The standard factory calibration consists of a
piston phone calibration at 250 Hz. This is expressed as dB re 1V / uPa.
A typical value is 177.0
dB re. 1 μPa/V
.
End-to-end System Calibration
To determine the end-to-end (overall) system calibration simply add the recorder and hydrophone
calibrations together. Eg -1.8 dB + 177.0 dB = 175.2 dB re 1 uPa.
Obtaining the calibration values
Calibration data is not shipped with the recorder, but instead made available online from the
calibration page of the Ocean Instruments website. To find the values for your recorder and
hydrophone simply enter their serial numbers into the website here:
http://www.oceaninstruments.co.nz/
The hydrophone serial number is usually printed on both the hydrophone bulb and the wet
connector collar. The recorder serial number can be found in the SoundTrap Host software.
Applying the calibration
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
Содержание SoundTrap ST500
Страница 1: ...SoundTrap ST500 User Guide May 2019...
