Utilização de filtros adaptativos em sistemas de redução ativa de ruído para ambientes amplos

Abstract

Industrial noise is a worrysome occupational health and safety subject-matter for employees. Prolonged exposure to noise may generate hearing loss or even heart or psychological problems. This study aims to evaluate the feasibility of an active noise control system to reduce sound pressure level generated by rotary machines in broad environments. The system works through the generation of an anti-sound that, when colliding with the unwanted noise, generates regions of destructive interference, reducing the sound intensity level. This anti-sound is generated through a control software with digital filters, that correct the phase and amplitude of a reference signal, in order to obtain the lowest resulting sound amplitude in the merging point of the wavefronts.Experimental results obtained in two rooms are also presented, showing the technique performance, mainly when applied to low frequencies. In a 200 Hz tonal noise, it was possible to reduce the overall ambient noise in 9,1 dB (reduction of 87,7% of sound intensity), with maximum attenuation points of 34,5 dB (reduction of 99,96% of sound intensity) in the error microphone region.