The minimum power output of free field point sources and the active control of sound

In this paper, a modified cost function is proposed in order to achieve the maximum noise attenuation using a set of secondary sources for a harmonically excited sound field. The modified cost function drives the error signal to the optimally attenuated sound field instead of minimizing the squared pressure. Moreover, changing the value to which the error signals must be driven allows change of the control strategy from global to local. The modified cost function requires the knowledge of the attenuated sound field, which is a condition that is well suited to narrowband noises, as is the case of turboprops. A numerical example of the application of the cost function is carried out using a finite element model/boundary element model of a real turboprop, with the goal of minimizing the interior sound field in the cabin to about 17 m 3 . A maximum averaged attenuation of 7 dB at blade-passage frequencies is achieved using six secondary sources and six error sensors, and 11 dB around the head of a seated crew member if the control system is tuned to achieve local control. = acoustic pressure after minimizing the weighted potential energy p Ω = acoustic pressure inside the local volume p 0 = acoustic pressure after minimizing the potential energy q s = secondary source strength q sJ = secondary source strength to minimize the cost function q sΩ = secondary source strength to minimize the local potential energy q s0 = secondary source strength to minimize the potential energy q α0 = secondary source strength to minimize the weighted potential energy V = volume of the enclosure x = location of error sensors y = location of sources α = potential energy weighting factor ΔE p0 = attenuation loss ρ 0 = air density ϕ = phase of the acoustic pressure ψ = acoustic mode shape Ω = local volume ω = angular frequency ω n = eigenfrequency

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“…Following the development of Nelson et al [22], the set of secondary source strengths that minimize this cost function is…”

Section: A Minimization Of the Squared Pressurementioning

confidence: 99%

Optimization of the Active Control of Turboprop Cabin Noise

Garbí

Palacios

Balastegui

et al. 2015

Journal of Aircraft

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“…The origin of the global coordinate system coincides with the sphere centre. The CV is 10×16×8 cm 3 and it has been meshed by 140 nodes and 72 8-nodes brick elements. Figure 8 shows the variation of the cost function versus the x 1 -coordinate of the CV centre for four different frequencies (109, 273, 546, 1092 Hz) and within 1.845 m from the secondary source centre.…”

Section: Optimum Locationmentioning

confidence: 99%

A BEM sensitivity formulation for three‐dimensional active noise control

Brancati

Aliabadi

Mallardo

2012

Numerical Meth Engineering

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Abstract. In this paper a novel Boundary Element (BE) formulation for sensitivity analysis of local active noise control in a three-dimensional field is presented. The formulation is based on the Helmholtz differential equation and it is valid for internal as well as for scattering wave propagation problems. The primary noise is attenuated within an enclosure, called control volume, by adding a control source modelled as an object with a vibrating surface. Both the optimum position of the control volume and the optimum location/orientation of the secondary source are determined by minimisation of a suitable cost function. The sensitivities are determined by implicit differentiation. A hierarchical adaptive cross approximation approach in conjunction with the GMRES solver is implemented to accelerate the convergence. Four numerical examples are presented to demonstrate accuracy and efficiency of the proposed formulations.

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“…A number of publications are also devoted to the optimization of the strength of the spatially distributed controls in order to minimize a quadratic pressure cost function. 3,4 In recent years, different approaches have been suggested to realize real-time active noise control (see, e.g., Refs. [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

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

Lim

Utyuzhnikov

Lam

et al. 2014

The Journal of the Acoustical Society of America

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This paper extends a potential-based approach to active noise shielding with preservation of wanted sound in three-dimensional settings. The approach, which was described in a previous publication [Lim et al., J. Acoust. Soc. Am. 129(2), 717-725 (2011)], provides several significant advantages over conventional noise control methods. Most significantly, the methodology does not require any information including the characterization of sources, impedance boundary conditions and surrounding medium, and that the methodology automatically differentiates between the wanted and unwanted sound components. The previous publication proved the concept in one-dimensional conditions. In this paper, the approach for more realistic conditions is studied by numerical simulation and experimental validation in three-dimensional cases. The results provide a guideline to the implementation of the active shielding method with practical three-dimensional conditions. Through numerical simulation it is demonstrated that while leaving the wanted sound unchanged, the developed approach offers selective volumetric noise cancellation within a targeted domain. In addition, the method is implemented in a three-dimensional experiment with a white noise source in a semi-anechoic chamber. The experimental study identifies practical difficulties and limitations in the use of the approach for real applications.

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The minimum power output of free field point sources and the active control of sound

Cited by 100 publications

References 6 publications

Optimization of the Active Control of Turboprop Cabin Noise

Optimization of the Active Control of Turboprop Cabin Noise

A BEM sensitivity formulation for three‐dimensional active noise control

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

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