Control of tonal noise from subsonic axial fan. Part 2: active control simulations and experiments in free field

Gérard, Anthony; Berry, Alain; Masson, Patrice

doi:10.1016/j.jsv.2005.01.022

Cited by 17 publications

(18 citation statements)

References 11 publications

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“…The integral of Equation 2 has been extensively studied due to its relevance to rotor acoustics and, under suitable conditions, as a good approximation to radiation from ducts. Many problems in source identification [1,2,5,6,7,8,9,10] can be viewed as attempts to recover the source term s n (r 1 ) from measurements of p n . The remainder of this paper consists of an analysis of the integral of Equation 2, which will establish limits on the information about the source which is radiated into the acoustic field, thereby fixing how accurately a source can be identified.…”

Section: Discussionmentioning

confidence: 99%

“…The source which generates such fields can be represented as a set of modes which vary with azimuth on a circular disk, whether or not the source includes a spinning element. Examples include rotating systems such as cooling fans [1,2], helicopter rotors [3,4] duct terminations such as aircraft engine intakes [5,6,7,8,9,10] and jets [11] if a jet is modelled as a distribution of disk-shaped sources.…”

Section: Introductionmentioning

confidence: 99%

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Inversion of spinning sound fields

Carley¹

2009

The Journal of the Acoustical Society of America

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A method is presented for the reconstruction of rotating monopole source distributions using acoustic pressures measured on a sideline parallel to the source axis. The method requires no a priori assumptions about the source other than that its strength at the frequency of interest varies sinusoidally in azimuth on the source disk so that the radiated acoustic field is composed of a single circumferential mode. When multiple azimuthal modes are present, the acoustic field can be decomposed into azimuthal modes and the method applied to each mode in sequence. The method proceeds in two stages, first finding an intermediate line source derived from the source distribution and then inverting this line source to find the radial variation in source strength. A far-field form of the radiation integrals is derived, showing that the far-field pressure is a band-limited Fourier transform of the line source, establishing a limit on the quality of source reconstruction, which can be achieved using far-field measurements. The method is applied to simulated data representing wind-tunnel testing of a ducted rotor system (tip Mach number of 0.74) and to control of noise from an automotive cooling fan (tip Mach number of 0.14), studies which have appeared in the literature of source identification.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Inversion of spinning sound fields

Carley¹

2009

The Journal of the Acoustical Society of America

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“…The motivation for the work presented in this paper is connected with previous work investigating the active control of small axial cooling fans, which can be characterized as compact acoustic sources. Active noise control of axial cooling fans has been studied using various control source configurations [1][2][3][4][5][6][7][8] . The range of control system configurations includes simple single control source configurations [1][2][3] to four control sources in various configurations [5][6][7] .…”

Section: Introductionmentioning

confidence: 99%

Characterization of microphone placement and noise sensitivity in a global active noise control system for a compact noise source

Rust¹,

Sommerfeldt²,

Gee³

et al. 2013

noise cont engng j

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This paper presents a sensitivity analysis to error microphone placement and extraneous noise sources for two control source configurations used for the active control of noise radiated from a compact source. The two control configurations analyzed are a linear array of four control sources with the primary source in the middle of the array and a symmetric array of four control sources surrounding the primary source. For modeling purposes, the primary source and the control sources are modeled as simple sources with a baffled free space Green's function to predict the noise measured by the four error microphones. The control source strengths which minimize the squared pressure at the error microphones are solved for based on error microphone locations. If the microphones are placed properly with no error in spatial location, this minimization process has been previously shown to result in radiated power minimization. Simulation results show the linear array is significantly more sensitive to microphone placement errors than the symmetric array. The linear array configuration is also shown to be more sensitive to added random noise in the error signals. Experimental results suggest that for the configurations used, the sensitivity to microphone placement errors was the dominant effect. The reduction in performance for the linear array configuration is significant with microphone placement errors and/or added random noise, while the reduction in performance for the symmetric array is minimal.

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“…In this case, the requirement is to extract information about source strength and directivity, but there is no need to know which processes generate the source. A second motivation, however, is the identification of the noisiest parts of the source with a view to reduction of noise at source, for example the identification of "hot spots" caused by unsteady loading on a cooling fan [11,12]. In this case, the link between the aerodynamics and the source is an essential part of the solution of the problem.…”

Section: Introductionmentioning

confidence: 99%

The radiating part of circular sources

Carley¹

2011

The Journal of the Acoustical Society of America

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An analysis is developed linking the form of the sound field from a circular source to the radial structure of the source, without recourse to far-field or other approximations. It is found that the information radiated into the field is limited, with the limit fixed by the wavenumber of the source multiplied by the source radius (Helmholtz number). The acoustic field is found in terms of the elementary fields generated by a set of line sources whose form is given by Chebyshev polynomials of the second kind and whose amplitude is found to be given by weighted integrals of the radial source term. The analysis is developed for tonal sources, such as rotors, and for Helmholtz number less than two, for random disk sources. In this case, the analysis yields the cross-spectrum between two points in the acoustic field. The analysis is applied to the problems of tonal radiation, random source radiation as a model problem for jet noise, and to noise cancellation, as in active control of noise from rotors. It is found that the approach gives an accurate model for the radiation problem and explicitly identifies those parts of a source which radiate.

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Control of tonal noise from subsonic axial fan. Part 2: active control simulations and experiments in free field

Cited by 17 publications

References 11 publications

Inversion of spinning sound fields

Inversion of spinning sound fields

Characterization of microphone placement and noise sensitivity in a global active noise control system for a compact noise source

The radiating part of circular sources

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