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Sonobuoy data for the 2012 Blue Whale Voyages

This dataset contains acoustic recordings from Directional Frequency Analysis and Recording (DIFAR) sonobuoys that were deployed throughout the 2012 Blue Whale Voyages conducted off Portland, Victoria, Australia from January – March (in the Bonney Upwelling). During the 20 days at sea 131 AN/SSQ-53D sonobuoys were deployed yielding more than 500 hours of acoustic recordings. In January a total team of three dedicated acousticians monitored round-the-clock for blue whales and in all weather conditions. In March the team size was increased so that five acousticians monitored and tracked blue whales round-the-clock. The recording chain for all sonobuoy deployments through 25 March 2012 included a 3-dB communications antenna with a central frequency at 161 MHz and masthead amplifier connected to a passive four way splitter. The highest point of the antenna was approximately 14 m above sea level. The antenna, amplifier, and splitter were connected with low loss cable, and each output of the four way splitter connected to the DIFAR input of a WiNRaDiO 2902i sonobuoy VHF receiver. On 25 March the masthead amplifier failed and was removed from the recording chain. This failure prompted the use of recently acquired WiNRaDiO G39WSBe sonobuoy receivers. The A/D converter used throughout both voyages was a RME Fireface UFX. The voltage outputs of all of the sonobuoy receivers were calibrated as a function of modulation frequency before the voyage, and DIFAR outputs from each of the 2902i and G39WSBe were connected to an instrument input of the UFX. The instrument inputs of the UFX (analog inputs 9-12) have a peak-peak voltage range of 80 V with digitally controlled gain that can be set between 10-65 dB, and this setting was noted in the Sonobuoy Deployment Log (see below) in order to measure received sound-pressure levels accurately. The digitised signals from the UFX were saved as 16-bit WAV files with 48 kHz sample rate using passive acoustic monitoring software Pamguard. Directional calibration The magnetic compass in each sonobuoy was calibrated/validated upon deployment as described by Miller et al. (2015, 2016). Calibration procedure involved measuring the mean bearing error and standard deviation of errors between the GPS-derived bearing from the sonobuoy to the ship and the magnetic bearing to the ship noise detected by the sonobuoy. 15-30 bearings were used for each calibration as the ship steamed directly away from the deployment location. Intensity calibration Obtaining calibrated intensity measurements from sonobuoys not only requires knowledge of the sensitivity of the hydrophone, but also the calibration parameters of the radio transmitter and radio receiver. Throughout the voyage, a hydrophone sensitivity of -122 dB re 1 V/µPa was applied to recordings via the Hydrophone Array Manager in PAMGuard. This value is defined in the DIFAR specification as the reference intensity at 100 Hz that will generate a frequency deviation of 25 kHz (Maranda 2001), thus the specification combines the hydrophone sensitivity and transmitter calibration. In line with manufacturers specifications, the WiNRADiO G39 WSB and 2902i both had a measured voltage response of approximately 1 V-peak–peak (approximately -3 dB) at 25 kHz frequency deviation (Miller et al. 2014), and this can be subtracted from the hydrophone sensitivity to yield an total combined factor of 125 dB re 1 V/µPa. These calibration settings, along with the shaped filter response provided by Greene et al. (2004) make it possible to obtain calibrated pressure amplitude from the recorded WAV audio files. Sonobuoy deployment metadata (Sonobuoy deployment log) This spreadsheet contains metadata on the deployment of sonobuoys deployed during the 2013 Antarctic Blue Whale Voyage. The first row contains column headers, while each subsequent row contains deployment information for a single sonobuoy. Information contained in each column are: buoyID: Buoy ID number is the sequential number