25 Mar 1974
- waterbody:North Atlantic OceanGrand Turk Island; U.S. Naval Facility
NOTES: Notes on tape: "1330 Zulu 25Mar1974" [MLNS notes: Low level thumps throughout, with several louder thump trains interspersed. Notes indicate low background level; however, this recording has very high ambient noise relative to any signals... perhaps tape was mislabeled?] Notes from analysis log: "Cassette number side up - rewind. Ambient level low - hear 'fog horn'-like reference signal clear, (appears that this signal is in 3-4 graduating levels spaced about 15 seconds apart). We were hearing the loudest or strongest one (every 3 min) now it is clear enough to hear the 15", 40" + 55" second levels) This could be systems (hydrophone) calibration method? Humpback: Pos.; No. Calling: 1? No. Full Calls: N.A. Need for further analysis: No. Notes: at 241 hear distant humpback portion of call, again at 448. Minke: Pos.; No. Heard: 2-3? No. Trains: 17. Need for further analysis: No. Notes: Have thump trains 030, 064, 113, 147, 197, 231, 343, 352, 379, 483, 542, 576, 592, 648, 706, 750, 782, Thump trains at various audio levels. Background is low, lets us hear more thump trains."
[Notes from analysis log for all tapes in the GRANDTURKS series: "Six half-hour background recording samples on selected days for a period of 53 days... to detect the arrival and departure of the Humpback whales (via sounds) for the season in the Caribbean Sea, Mouchier, Navidad and Silver Banks...There are indications that recordings used a 420Hz Low Pass Filter. Recording equipment used was a Realistic model CTR-19. Cassette recorder operating on 110VAC, Freq 60-10,000Ha.. The Realistic recorder is poor recording frequencies below 60Hz as evidenced by spec sheet and sonograms. There is 120 & 180Hz electrical interference 'splatter' on some tapes. In certain cases when the ambient is low, the gain of the systems are raised hence we have heavy interference masking wanted signals. This could be caused by a fluorescent light fixture near the recording system? I doubt that it is in the hydrophone pre-amp network." See analysis log for more details.] SEAOCEAN