31 Dec 1973
- waterbody:North Atlantic OceanGrand Turk Island; U.S. Naval Facility
NOTES: Notes on tape: "Time: 1200 Zulu." [MLNS notes: low level thumps throughout, with several louder trains - at 0:27, 9:45, and 15:18.] Notes from analysis log: "Cassette number side up - rewind. Ambient level low, distant ship traffic in background. Hear weak pinging off and on throughout recording, ASW ship. Humpback: Neg.; Minke: Pos.; No. Heard: [blank]; No. Trains: 5+. Need for further analysis: Yes - explore the very low thumps. Notes: At 178, good level thump train, long. At 235 there is 2-3 blast type thumps preceding intermittent train - should look into these, At 418 a good loud thump train, long too. At 460 are short, strong train, - not a full train. At 509 a weak train in background."
[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