Broad Band Noise

Sound classed as noise which has its energy distributed over a large section of the audible range. Also called wideband noise, and the opposite of narrow band noise.

See: Spectrum. Compare: Background Noise, Gaussian Noise, Infrasonic, White Noise.

The output of most ventilation ducts is an example of steady broad band noise, and a jet engine flyover could be classed as transient broad band noise. Most motors, including those in household appliances, produce a great deal of such noise, often with much of its energy in the higher frequency region where the human ear is the most sensitive (1 to 4 kHz). This aspect of the sound is not given special account in decibel measurements, and thus such measurement systems as the Perceived Noise Level, Noise Rating, and Noise Criterion, and their derivatives and extensions have been devised.

Third-octave spectrum analyses of various broad-band sound sources, some natural, others manmade.

Left: Campus ambience, outdoors, outside University of British Columbia's Sedgewick Library. Tonal centres come from construction work in distance and from ventilation ducts atop a nearby building.

Right: Mechanical noise from ventilation equipment atop the Buchanan Building, U.B.C.

Left: Office ambience, Buchanan Building, U.B.C., near ventilation duct in corridor.

Right: Surf, Wreck Beach, Vancouver.

Left: Domed horticultural space, flowing water, tropical plants and birds, MacMillan Conservatory, Vancouver.

Right: Wilderness lakeside ambience, Princess Lake, Jasper National Park, Alberta.