Alfred J. Bedard, Jr.
Natl. Oceanic and Atmospheric Admin., Environmental Technol. Lab., 325 Broadway, Boulder, CO 80303
Low-frequency sounds from both natural and civilization sources can travel for long distances (tens or hundreds of kilometers), producing local regions of enhanced as well as reduced intensity depending upon range and time. Thus the identification of sources can be difficult, since merely mapping sound level in the direction of increasing intensity may not help to identify distant sources. A brief review of some examples of low-frequency background sounds provides the basis for a discussion of potential methods for identifying sound sources in a complex propagation environment. At low frequencies (<100 Hz) it is more difficult to determine direction with simple, portable systems. Some practical approaches for low-frequency source location are described.