19 Dec 1973
- waterbody:North Atlantic OceanGrand Turk Island; U.S. Naval Facility
NOTES: Notes from analysis log: Time:0502Zulu 19Dec73. Ambient level moderate. At 352 there is some "open mike" room noise? door shut. Humpback: negative. Minke: positive. No. heard: 1? No. TRAIN: 5. Need for further analysis? Yes. Notes: at 030 thump train, moderate level, again at 197 again at 432 a good clear and long sample - has lot of clipped off high frequency components. At 628 another strong and long train, - at 701 a weaker train, short.
[MLNS notes: Obvious thump trains at 0:31, 5:33, 9:45, 14:55, 24:23, and 28:25. Several thumps may be heard throughout between the more obvious thump trains, although difficult to hear due to ambient and equipment noise. These thumps sound and look (on spectrogram) like the minke thumps. 23Nov2003CB]
[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