Accession Number : AD0699188

Title :   PROPAGATION OF SOUND THROUGH ATMOSPHERIC FOG,

Corporate Author : BROWN UNIV PROVIDENCE R I DIV OF ENGINEERING

Personal Author(s) : Cole,John E. , III ; Dobbins,Richard A.

Report Date : DEC 1969

Pagination or Media Count : 36

Abstract : The propagation of sound in an atmospheric fog is described by considering a system of liquid droplets suspended in a mixture of their vapor and an inert gas. The perturbation of this system by a sound field causes the droplets to exchange mass, momentum, and heat with the surrounding gaseous mixture and results in acoustic attenuation and dispersion. Strong attenuation per unit wavelength due to mass transfer effects is predicted in the subaudible (infrasonic) region in which signals from weather fronts and atmospheric explosions are monitored. Dimensional attenuation is found to be nearly constant both for low audible frequencies and for high frequencies. The level of dimensional attenuation for the high frequencies is approximately six times that at the low frequency level. Transition from the low level to the high level of attenuation depends on fog particle size. Computed results for typical fog data are given, and optimal signaling frequencies are discussed. (Author)

Descriptors :   (*FOG, *SOUND TRANSMISSION), ATTENUATION, ATMOSPHERE MODELS, AEROSOLS, PARTICLE SIZE, FREQUENCY, MASS TRANSFER, TRANSPORT PROPERTIES, RARE GASES, DIFFUSIVITY, THERMAL PROPERTIES, HUMIDITY

Subject Categories : Atmospheric Physics
      Acoustic Detection and Detectors
      Acoustics

Distribution Statement : APPROVED FOR PUBLIC RELEASE