An optimal local active noise control method based on stochastic finite element models

Abstract

An optimal local active noise control method based on stochastic finite element models Airaksinen, T.; Toivanen, J.Airaksinen, T. & Toivanen, J. (2013). An optimal local active noise control method based on stochastic finite element models. Journal of Sound and Vibration, 332 (2013) pp.6924-6933. doi:10.1016/j.jsv.2013 AbstractA new method is presented to obtain a local active noise control that is optimal in stochastic environment. The method uses numerical acoustical modeling that is performed in the frequency domain by using a sequence of finite element discretizations of the Helmholtz equation. The stochasticity of domain geometry and primary noise source is considered. Reference signals from an array of microphones are mapped to secondary loudspeakers, by an off-line optimized linear mapping. The frequency dependent linear mapping is optimized to minimize the expected value of error in a quiet zone, which is approximated by the numerical model and can be interpreted as a stochastic virtual microphone. A least squares formulation leads to a quadratic optimization problem. The presented active noise control method gives robust and efficient noise attenuation, which is demonstrated by a numerical study in a passenger car cabin. The numerical results demonstrate that a significant, stable local noise attenuation of 20-32 dB can be obtained at lower frequencies (< 500 Hz) by two microphones, and 8-36 dB attenuation at frequencies up to 1000 Hz, when 8 microphones are used.

Active control of vehicle’s interior sound field by using multichannel H∞ robust controller

“…The amounts of absorption coefficients of each panel have been extracted from a previous study. 10 There is at least one driver in the car, and it is likely that there are four occupants. The presence of these occupants and their movements might change the frequency response of sound pressure at the occupants' ears.…”

“…A local noise reduction of 20–32 dB on the driver’s ears has been obtained. 10 Cheer and Eliot also devised a multichannel ANC system for a car by considering the uncertainties caused by inaccuracy in modeling and changing the number of occupants. The overall design of the controller could minimize the sum of the squares of the microphone error signals with such constraints as robust stability, the limitation of the increased sound level, and open-loop controller stability.…”

Portable Low-Frequency Noise Reduction Device for Both Small Open and Closed Spaces

“…On the axis, we select 5 testing points with an interval of 5 cm ((0, 5), (0, 10)⋅ ⋅ ⋅ (0, 25)). In order to simulate the inverted cone space, the other three points including (10,5), (20,10), and (30,15) are added in this testing. According to the axis-symmetric principle, we use the test results of the three test points instead of the test results of conical surface.…”

“…Kwon and Park propose an active window system, which uses a feedforward control method for active noise control, to reduce the exterior noise sources, such as traffic noise and construction noise which enter rooms through open windows used for natural ventilation [19]. Airaksinen and Toivanen present a new method by using numerical acoustical modeling to obtain a local active noise control that is optimal in stochastic environment [20]. Tanaka deals with local as well as global ANC using a parametric array loudspeaker (PAL) possessing intriguing properties: sharp directivity, low sound pressure decay by distance, and capability of steering directivity [21].…”