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Nonlinear Superposition of Repetitive Noise Sources
Saira Akhtar, Esmat Kalair, Naeem Abas and Nasrullah Khan

Noise pollution is viewed as a modern plague. Modernization’s bullwhip has returned as sonic boomerang to avant-garde civilization. World community has punitive laws against gun powder explosives but no edict against sonic bullets. Large noisy machines include airplanes, railway, two stroke engines, loud speakers, fire crackers and power generators during load shedding. Random superposition of multiple sounds can produce sudden loud shrieking noisy sonic bullets. This paper points out potent noise sources, coherent superposition of noise and sound intensification effects of short duration repetitive sounds. When period between two successive sounds decrease below 100ms human ears hear spiraling sounds. This paper presents a model of random noise amplification by superposition of multiple sounds and accumulative aftereffect of the repetitively pulsed sounds. It is simulated to show the sound intensity increases more than simple logarithmic addition when the time interval between two successive sounds is less than persistence time of human ear.

Keywords: Noise pollution, Superposition, Interference, Repetitive noise

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