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Title: A magnetic tape wave recorder and energy spectrum analyzer for the analysis of ocean wave records
Authors: New York University
United States. Army. Office of the Chief of Engineers
Chang, Sheldon S. L.
Keywords: Ocean waves
Spectrum analysis
Publisher: United States, Beach Erosion Board
Engineer Research and Development Center (U.S.)
Series/Report no.: Technical memorandum (United States. Beach Erosion Board) ; no. 58.
Description: Technical Memorandum
From the Introduction: The essential purposes of the ocean wave recorder and the ocean wave analyzer are to obtain a wave record on magnetic tape, to reproduce the record on chart paper, and to produce from the magnetic tape record a power (energy) density spectrum as a function of frequency. The power density spectra of the recorded waves so obtained are to be used for the study of the effects of waves in beach erosion. The instrument analyzes a twenty minute wave record in approximately 3 minutes and records the resulting power spectrum on chart paper. The power in an ocean wave is concentrated in a frequency range well below 0.5 cycle per second, and the instrument is capable of separating frequency components 0.005 cycle per second apart. Because of the low frequency of the ocean wave, it is necessary to speed up the wave record a few thousand times to play back the recorded frequency in the audio-frequency range. This is accomplished without noticeable distortion by using the ocean wave signal to frequency modulate a 6 cps carrier, and to record the modulated wave on magnetic tape which is then played back at a speed 4,000 times the speed of the original recording. The increased carrier frequency is then detected with a chain of pulse circuits similar to those employed in a frequency meter. A photograph of the instrument is shown in Figure 1, and a block diagram is shown in Figure 2.
Rights: Approved for Public Release, Distribution is Unlimited
Appears in Collections:Technical Memorandum

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