% DSGex
%
% Demonstrates reading in DSG files, converting to Pascals, and calculating
% dB-rms and spectrum level power spectrum
%
% 2011- David Mann, Loggerhead Instruments
% www.loggerheadinstruments.com

% The following are the hydrophone and DSG calibration settings
% These may need to be modified based on the setup
hydro_cal=-186;  %hydrophone calibration e.g. -186 dBV/uPa
DSG_gain=20; % gain on DSG; 20 dB is default

% Select dsg file to load
[FileName,PathName,FilterIndex] = uigetfile({'*.dsg','DSG files (*.dsg)'},'Select a dsg file');
    if isequal(FileName,0)|isequal(PathName,0)
        return
    end
    
 cd(PathName);


% Load DSG file
% DF_HEAD and SID_SPEC are structures with file information 
% (e.g. sample rate, record date and time)
% datacat are data strung together and scaled to +/-1 by MATLAB
[DF_HEAD,SID_SPEC,totrecs,datacat]=DSGread(FileName,0,0);

% convert to Pa
VoltsPerPa=1000000*power(10,(hydro_cal+DSG_gain)/20);
datacat=datacat/VoltsPerPa;

% plot
srate=1000000/(SID_SPEC.SP256/256);
t=[0:length(datacat)-1]/srate;  %create time scale
figure(1)
plot(t,datacat);
xlabel('Time (s)');
ylabel('Sound Level (Pa)');


% Calculate rms SPL (dB re 1uPa)
rmsdB=20*log10(std(1000000*(datacat-mean(datacat))))  %calculate dB re 1uPa

% Calculate FFT using entire signal length
freqres=srate/length(datacat); %frequency resolution
hpts=floor(length(datacat)/2);  %half of the number of FFT points
DATACAT = abs(fft(datacat*1000000))/hpts; %calculate FFT and scale by half points in FFT
DATACAT=20*log10(DATACAT); % convert to dB re 1 uPa
DATACAT= DATACAT -(10*log10(freqres));  %scale to spectrum level

% Plot Spectrum Level
f=[0:hpts-1]*freqres;  %create frequency scale
figure(2)
plot(f,DATACAT(1:hpts));  %plot first half of spectrum
xlabel('Frequency (Hz)');
ylabel('Amplitude dB re 1uPa^2/Hz');