Experimental Validation of the Active Noise Control Methodology Based on Difference Potentials

Abstract

To achieve active noise cancellation over a large area, it is often necessary to get a measure of the physical properties of the noise source to devise a counter measure. This, however, is not practical in many cases. A mathematical approach, the difference potential method, can provide an alternative solution for active shielding over a large area. In this approach, the cancellation of unwanted noise requires only measurements near the boundary surface but not at the source itself, and no other information is required. Moreover, the solution based on difference potentials applies to bounded domains in the presence of acoustic sources inside the domain to be shielded. This paper reports on the results of experimental validation for the methodology. It has been demonstrated that while preserving the wanted sound, the developed approach can cancel out the unwanted noise. The volumetric noise cancellation offered by the proposed methodology, along with leaving the wanted sound unchanged, is a unique feature compared with other techniques available in the literature. It can be most useful in the context of applications related to civil aviation, in particular, for eliminating the exterior noise inside the passenger compartments for both current and future generations of commercial aircraft.

Potential-based methodology for active sound control in three dimensional settings

“…23, an AS system with these errors should allow us to achieve about 50-55 dB attenuation. 25 This is indeed consistent with the attenuation we obtained in the numerical analysis. The corresponding time delay error, which can be caused by the DSP apparatus, is below 8 lsec.…”

“…In addition, the control outputs are supposed to be accurately separable from the input data. The experiments confirm that the potential-based ASC method, validated in one-dimensional conditions, 22,25 can be extended to cover full three-dimensional acoustic conditions and achieve global noise cancellation while preserving the wanted sound.…”

Multi-domain active sound control and noise shielding

“…The low attenuation between 580 and 700 Hz is another example of very small sound pressures at the boundary of the shielded domain at those frequencies when the boundary is close to the nodal plane of the predominant resonant mode. Overall, the result shows that the general solution which was used for the experiments with pure tone sources 20 is also effective with broadband noise, as long as the sound field is strong enough to be measured accurately at the boundary of the shielded domain.…”

“…The solution for the AS problems either with or without the wanted sounds have previously been experimentally validated with pure tone sound sources in a duct, and the results were reported in Ref. 20. Following this work, the experiment is now extended to cover broadband sound fields, including multiple resonance regions.…”

Boundary element method based on preliminary discretization

“…This method is based on discrete projections. It was used for active noise suppression [9]. The closest ideas to this work were published in [10].…”