Accession Number:

ADA275387

Title:

Attenuation of Outdoor Sound Propagation Levels by a Snow Cover

Descriptive Note:

Corporate Author:

COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH

Personal Author(s):

Report Date:

1993-11-01

Pagination or Media Count:

110.0

Abstract:

The absorption of sound energy by the ground has been studied extensively because of its importance in understanding noise propagation through the atmosphere. This report investigates the attenuative effect of snow on sound propagation, and provides, quantitative measurements and an accurate model for predicting these effects. Summer and winter experiments were conducted at a site in northern Vermont to investigate the effect of a snow cover on low energy sound propagation in the 5- to 500-Hz frequency band for propagation distances between 1 and 274 m. Pistol shots were used as the source of the acoustic waves, with geophones and microphones serving as the receivers. A comparison of the summer and winter recordings revealed a number of effects caused by the introduction of a 0.25-m-thick snow cover. The peak amplitude of the air wave was more strongly attenuated in the winter, with a decay rate proportional to r exp-1.6 versus r exp-1.2 in the summer, corresponding to an order of magnitude difference in the signal levels after 100 m of propagation. The waveforms were also markedly changed, with broadened pulses and greatly enhanced low frequencies appearing in the winter recordings. The pulse broadening and peak amplitude decay rates of the acoustic waveforms were successfully predicted theoretically using a layered, rigid, porous model of the snow, with an assumed surface effective flow resistivity of 20 kN sm to the 4th. Calculations of ground motion induced by the atmospheric sound waves were made using a viscoelastic model of the ground and the wavenumber integration technique. Although soil ground motions were Acoustic to seismic coupling, Sound absorption, Outdoor sound propagation, Snow acoustics, Porous medium acoustics.

Subject Categories:

  • Soil Mechanics
  • Snow, Ice and Permafrost
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE