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Drum Recorder.
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An instrument that would provide a continuous visual picture of sounds received at a hydrophone.
The SOFAR drum recorders were operational 24 hours a day, 365 days/year.
The SOFAR drum recorders were operational 24 hours a day, 365 days/year.
A major component of the machine was the cylinder, with a circumference of about 36” and a width of about 12”, around which a piece of heat-sensitive paper was wrapped. This cylinder rotated slowly, completing one revolution in 30 minutes.
A hot-wire pen was used to trace a line on the paper as the cylinder rotated. This pen was connected to an amplifier, so that whenever a sound was received from the hydrophone, the pen would jiggle accordingly, leaving a noticeable trace. At the start of the 24-hour recording session, the pen would be
positioned at the left hand end of the cylinder. A gear mechanism would very slowly move this pen from left to right, taking 24 hours to move from the left hand side of the cylinder to the right hand side of the cylinder. As the cylinder made a complete revolution, the pen would have gradually moved ¼” to the right.
Click the link below to see a drum recorder in action!!
A hot-wire pen was used to trace a line on the paper as the cylinder rotated. This pen was connected to an amplifier, so that whenever a sound was received from the hydrophone, the pen would jiggle accordingly, leaving a noticeable trace. At the start of the 24-hour recording session, the pen would be
positioned at the left hand end of the cylinder. A gear mechanism would very slowly move this pen from left to right, taking 24 hours to move from the left hand side of the cylinder to the right hand side of the cylinder. As the cylinder made a complete revolution, the pen would have gradually moved ¼” to the right.
Click the link below to see a drum recorder in action!!
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Once the paper was removed and laid out flat, (36” wide and 12” from top to bottom), it would show a series of 48 parallel lines (with occasional squiggles showing sound activity), which could be read like a book, from left to right and down the page. There were ‘time marks’ on the recording, so that a fairly accurate time of the arrival of a sound could be determined, and further analysis performed using the
archived magnetic tapes. (Magnetic tape recordings of the hydrophone signals were also made 24/7, which could be used for much more detailed analysis ‘after the fact’.)
Posted 31st. Dec. 2013
archived magnetic tapes. (Magnetic tape recordings of the hydrophone signals were also made 24/7, which could be used for much more detailed analysis ‘after the fact’.)
Posted 31st. Dec. 2013
Posted 31st. Dec. 2013.