Variation in measured sound level as a function of propagation environment and distance

Abstract

The propagation environment exerts a large influence on the range of received levels of impulsive events. This talk focuses on the variation in excess attenuation over durations of less than approximately 15 minutes. Data are presented for greatly different measurement distances (25∼m to 7∼km) and propagation environments (sparse vegetation to forested), illustrating the effects of distance and terrain cover on sounds from a propane cannon and an artillery source. Over sparse vegetation 7∼km from an artillery source, the received CSEL varied 11∼dB within a 12-minute duration. In measurements up to approximately 300∼m from the source, variation in received level (both peak and SEL) was less than 0.5∼dB within the forest, and much more in the open. The control of the forest canopy on the micrometeorology seems to explain the effect. © 2008 Acoustical Society of America.