Accession Number : AD0434705


Title :   ACOUSTIC DETECTION OF HIGH - ALTITUDE TURBULENCE


Descriptive Note : Technical Report


Corporate Author : MICHIGAN UNIV ANN ARBOR ANN ARBOR United States


Personal Author(s) : Wescott,John W


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/434705.pdf


Report Date : 01 Mar 1964


Pagination or Media Count : 62


Abstract : Background noise at frequencies from 0.2 to 200 cps was monitored with free-floating, balloon-borne acoustic probes at altitudes of 55,000 to 73,000 feet. Spectrograms, signatures, cross-correlations, and probability-density curves were obtained from the data. The noise has a spectrum with 6 db/octave negative slope, is acoustic and Gaussian, and is time-steady for periods of several hours, although noise pressures from 0.03 to 1 dyne/sq. cm were measured on different days. These and other results indicate that the noise comes from lower altitudes and is produced by an array of statistically independent radiators, such as turbulent eddies. A theory for the power spectrum of noise radiated by turbulence is cited, and the predicted spectrum is compared to the experimental results. Other possible sources of high-altitude acoustic noise are described. Descriptions and illustrations of the instruments used to acquire and process the experimental data are presented.


Descriptors :   TURBULENCE , ACOUSTIC DETECTORS , HIGH ALTITUDE , DETECTION , SCIENTIFIC RESEARCH , NOISE , EXTREMELY LOW FREQUENCY , BALLOON EQUIPMENT , SPECTROSCOPY , CORRELATION TECHNIQUES , PROBABILITY , DENSITY , EXPERIMENTAL DATA


Distribution Statement : APPROVED FOR PUBLIC RELEASE