Detection of infrasound from natural and civilization sources: measurement of complex signal/noise environments

Detection of low-level, infrasonic sound waves in the presence of noise can require a combination of processing techniques depending upon the details of signal as well as noise characteristics. Forms of noise include local, nonacoustic pressure changes in the atmospheric boundary layer, natural sound sources (not of interest for some specific application), civilization sound sources (masking other sounds), instrumentation noise, and "noise" introduced by processing. Examples of the various noise types are presented together with techniques for identification and elimination. At higher infrasonic frequencies (e.g. between 1 and 10 Hz) a variety of promising geophysical applications are possible, yet sources are more frequent. Particular attention is given to this frequency range. Recent measurements correlating infrasonic signals with sprites and other transient luminescent phenomena will be used as an example of the potential of infrasound for geophysical remote sensing.