Outdoor sound source identification

A sound source localization system, comprising:

• multiple, physically unconnected, data acquisition units that are spatially distributed over an area of interest, each data acquisition unit having:
• (a) at least one microphone capable of sensing and measuring sound to obtain analog sound signals,
• (b) a receiver of transmitted messages from a satellite radio beacon positioning system, the receiver deriving position and time reference information from the messages,
• (c) at least one analog-to-digital converter (ADC) associated with a corresponding microphone to sample the analog sound signals to obtain corresponding digital acoustic data, and
• (d) a hardware logic circuit coupled to the ADC to receive the digital acoustic data therefrom and regularly time stamp batches of the digital acoustic data with a sub-microsecond accuracy relative to the time reference information derived from the receiver, and record a corresponding unit location from the position reference information derived by the receiver;
• and
• a data processing location for receiving digital acoustic data along with the unit location and time stamping information from each data acquisition unit, the data processing location configured to:
• (a) transform each of the digital acoustic data from each data acquisition unit from a time domain into a frequency domain to obtain a set of transformed acoustic signal data;
• (b) compute cross-spectra for multiple pairs of the transformed acoustic signal data;
• (c) transform the cross-spectra for each signal pair back into the time domain to obtain cross-correlation functions;
• (d) estimate from the time-domain cross-correlation functions respective time delays of sensed acoustic events identified from the measured sound signals between each pair of data acquisition units;
• and
• (e) determine a sound source location for each sensed acoustic event from the estimated time delays and recorded unit locations of each data acquisition unit pair.