System attractor dynamics for a low-frequency acoustical signal propagated in the atmosphere

Abstract

An experimental study of low-frequency propagation over flat terrain has been previously reported [J. Acoust. Soc. Am. Suppl. 1 86, S120 (1989)]. The sound pressure level of a 27.7-Hz acoustical source was monitored at a distance of 770 m, the level being recorded at 1-min intervals over a 5-day period in March 1989. Additional micrometeorological measurements of the turbulent momentum, heat, and moisture fluxes were made adjacent to the path, and a Doppler sodar was used to monitor the boundary layer wind profile. We have now analyzed the signal for the system attractor size, and found it to possess an unexpectedly small dimension of about 2.3. A low-order reconstruction of the dynamical phase space revealed that most of the measurements fell within a small portion of that space, but spurious noise on the microphone showed large excursions. Implications for signal smoothing, interpolation, or rejection that are based on reconstructed system dynamics are discussed and illustrated.