1 Apr 1974
- waterbody:North Atlantic OceanGrand Turk Island; U.S. Naval Facility
NOTES: Notes on tape: "1900 Zulu 1Apr1974" [MLNS notes: Low level thumps throughout, with several louder thump trains interspersed.] Notes from analysis log: "Cassette number side up - rewind. Ambient sea noise low. Portions of the 12-second Knock (repeated every 12 seconds) is on this tape. May be a research vessel using bottom profile thump gear, (air drive hammer). Next reel has more of it. Humpbacks: Pos.: No. Calling: 2; No. Full Calls: N.A. Need for further analysis: No. Notes: Hear umpback signals in background at start, getting stronger by 268, 500 echo effect here maybe transiting, - can hear 2 distinctly now 525 area, still not good enough for grams. Minke: Pos.; No. Heard: 2? No. Trains: 6; Need for further analysis: No. Notes: thump trains 105, 245 (at 317 a single knock is heard followed by several more) 335, 533, 700, 786. there are strong level single knocks toward end of reel (see next reel for explanation under mechanics)."
[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