Document Type : Original Article

Authors

• Farhad Forouharmajd ¹
• Parvin Nassiri ²
• Farshad Forouharmajd ²
• Masoumeh Ahmadvand ³

¹ Department of Occupational Health Engineering, School of Public Health, Isfahan University of Medical Sciences, Isfahan; Tehran University of Medical Sciences, Tehran, Iran

² Department of Occupational Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran

³ Fars Shasi Company, Montazerieh Industrial Park, Najaf Abad, Isfahan, Iran

Abstract

Aims: The object is to find a manner of reduction primary noise from a source by an electro acoustic device that cancels unwanted sound by generating an anti sound (anti noise) of equal amplitude and an opposite phase is described as an active noise control system. Materials and Methods: In this method, the primary noise is acquired via a microphone, and the anti noise propagates with the same amplitude and the reverse phase at the primary noise path via a speaker to cancel the original noise. The effectiveness of cancellation of the primary noise depends on the accuracy of the amplitude and phase of the generated anti noise. Results: The results present a noise reduction of 16 dB until 20 dB overall. A change in the system setup and noise power can reach a noise reduction up to 25 dB. Perhaps, this is due to the background noise and primary noise differences that create a powerful anti noise for canceling the original noise. Conclusions: With regard to the wide range of frequencies of different noise sources, having optimized circumstances in the duct, microphone location on the duct body or even the distance of the speakers may be important in signal processing, noise sampling and anti noise production.

Keywords

• Active noise control
• digital signal processing
• duct
• low frequency noise
• matrix laboratory simulation