21 Mar 1974
- waterbody:North Atlantic OceanGrand Turk Island; U.S. Naval Facility
NOTES: Notes on tape: "Time 1100 Zulu 21Mar1974" [MLNS notes: Low level thumps throughout, with several louder thump trains interspersed.] Notes from analysis log: "Cassette number side up, rewind. Ambient level low. Humpback: Pos.; No. Calling: 1? No. Full calls: N.A.; Need for further analysis: No. Notes: At 091 have Humpback part of call - not enough signal strength for grams, near 390 have few strong portions of a caller, gets better toward end of tape. Minke: Pos.; No. Heard: 2? No. Trains: 15; Need for further analysis: No. Notes: Have thump train at 112, 170, 234, 340, 370, 423, 460, 500, 541, 602, 619, 704, 732, 750, 763 at various audio levels."
[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