| Summary: | Progress Code: completed Statement: Sonobuoy recordings are calibrated for sound pressure level according to the standard sonobuoy frequency response specifications, and the recording gain on the receiving instruments. Recording gain is noted in the data log. Recordings made from sonobuoys deployed prior to CTD stations usually had a fair amount of vessel noise throughout as the sonobuoy was typically deployed between 3-6 nautical miles from the stations. Sonobuoys deployed during standard survey mode had a large amount of vessel noise initially, but this decreased rapidly as the ship moved away from the sonobuoy permitting clean recordings for the vast majority of sonobuoy recordings. The exception to this was when sonobuoys were deployed when the ship was in 'ice-breaking' mode. This increased the amount of vessel noise greatly throughout most of recordings. Data_Resolution Sonobuoys were deployed approximately every 30 minutes of latitude along N-S transects separated by 5 degrees of longitude, as well as opportunistically when whales were sighted. During the initial E-W transect (#12) across the top of the survey area, sonobuoys were deployed prior to most CTD sampling stations. Data Acquisition: DIFAR (DIrectional Fixing And Ranging) 53D sonobuoys were deployed every 30 minutes of longitude during each of the north-south sampling transects as part of the acoustic survey for marine mammals. Sonobuoys were also deployed opportunistically when large numbers of whales (in particular minke whales) were sighted. Additionally, on the initial E-W transect (#12) sonobouys were deployed prior to the majority of CTD stations. The VHF receiving system for the sonobuoys aboard the ship began with a 6 element YAGI antenna mounted atop the ship's mast. The sonobuoy's VHF signal output from the YAGI was amplified through an Advanced Receiver Research VHF amplifier and received on ICOM PCR-1000 VHF receivers modified to improve low frequency audio output. The audio signal passed through a low pass anti-alias filter ...
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