Dataset: West Bay 2011-2012 Acoustic Time Series: raw files
Deployment: West_Bay_Marine_Reserve

Beginning in June of 2011, a long-term effort was initiated to record ambient underwater sound within the West Bay Marine Reserve. This was accomplished using a low-power DSG acoustic recorder (Loggerhead Instruments, Sarasota, FL, USA) equipped with an off-the-shelf HTI-96 hydrophone with a sensitivity of -185.8 dBV/μPa and flat frequency response between ~0.1 and 30 kHz (High-Tech Inc., Gulfport Mississippi). The instrument was powered by a set of standard alkaline D-cell batteries. The data were digitized using a 16-bit resolution and written to a standard solid-state SD memory card. All components are housed in a 0.65 m long, 11.5 cm diameter PVC pressure case.

The instrument was deployed near the center of the West Bay Marine Reserve at a depth of ~3 m below MLLW and on an area of flat lying seabed ~10 m from surrounding oyster reef habitat. The pressure case was mounted vertically using a concrete anchor to position the hydrophone element ~1 m off the seabed. The tidal range within West Bay is small, typically <0.75 m.

A total of eight deployments were carried out using a single DSG recorder between 18 June 2011 and 06 July 2012. The resulting time series includes data collected on a total of 321 days over this 384-day monitoring period, which represents an 83% data return rate. Depending on the planned length of the deployment, the instrument was programmed to record for a 60 sec duration at 15-minute intervals, or for a duration of 30 sec at 30-minute intervals. A 50-kHz sampling rate was used for all deployments. The usable bandwidth of the data is taken to be ~0.1-20.0 kHz, as the DSG applies an anti-alias filter prior to A/D conversion. In total, 27,565 separate recordings were made as part of this monitoring initiative.

The data may be read into MATLAB using the included function DSGread.m (from Loggerhead Instruments).

Example:
% Set calibration and gain
hydro_cal=-185.8;
DSG_gain=10; % or 20

% Load DSG file
% DF_HEAD and SID_SPEC are structures with file information
% (e.g. 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 uPa
VoltsPeruPa=power(10,(hydro_cal+DSG_gain)/20);
datacat=datacat/VoltsPeruPa;

% 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 (uPa)');

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