Author
A.J. Bullmore
Bio: A.J. Bullmore is an academic researcher from University of Southampton. The author has contributed to research in topics: Harmonic & Sound power. The author has an hindex of 9, co-authored 9 publications receiving 654 citations.
Papers
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TL;DR: In this paper, an analysis of the effectiveness with which active methods can be used for producing global reductions in the amplitude of the pressure fluctuations in a harmonically excited enclosed sound field is presented.
156 citations
TL;DR: In this paper, the authors used the near field technique developed by Levine to calculate the total power output from an arbitrary number of point primary and secondary sources, which is a quadratic function of the complex strengths of the secondary point sources.
124 citations
TL;DR: In this article, it was shown that when a single mode dominates the response near optimal reductions in acoustic potential energy can be achieved by minimizing the pressure at a single sensor, provided that the source is placed at a maximum of the primary sound field.
114 citations
86 citations
TL;DR: In this article, the authors compared the measured results of active minimization experiments in an enclosed sound field with those predicted from theory, and found that the response of the experimental enclosure was very close to that predicted by the computer model when these problems were overcome.
72 citations
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01 Jun 1999
TL;DR: The basic adaptive algorithm for ANC is developed and analyzed based on single-channel broad-band feedforward control, then modified for narrow-bandFeedforward and adaptive feedback control, which are expanded to multiple-channel cases.
Abstract: Active noise control (ANC) is achieved by introducing a cancelling "antinoise" wave through an appropriate array of secondary sources. These secondary sources are interconnected through an electronic system using a specific signal processing algorithm for the particular cancellation scheme. ANC has application to a wide variety of problems in manufacturing, industrial operations, and consumer products. The emphasis of this paper is on the practical aspects of ANC systems in terms of adaptive signal processing and digital signal processing (DSP) implementation for real-world applications. In this paper, the basic adaptive algorithm for ANC is developed and analyzed based on single-channel broad-band feedforward control. This algorithm is then modified for narrow-band feedforward and adaptive feedback control. In turn, these single-channel ANC algorithms are expanded to multiple-channel cases. Various online secondary-path modeling techniques and special adaptive algorithms, such as lattice, frequency-domain, subband, and recursive-least-squares, are also introduced. Applications of these techniques to actual problems are highlighted by several examples.
1,254 citations
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TL;DR: The importance of having a clear understanding of the principles behind both the acoustics and the electrical control in order to appreciate the advantages and limitations of active noise control is emphasized.
Abstract: Active noise control exploits the long wavelengths associated with low frequency sound. It works on the principle of destructive interference between the sound fields generated by the original primary sound source and that due to other secondary sources, acoustic outputs of which can be controlled. The acoustic objectives of different active noise control systems and the electrical control methodologies that are used to achieve these objectives are examined. The importance of having a clear understanding of the principles behind both the acoustics and the electrical control in order to appreciate the advantages and limitations of active noise control is emphasized. A brief discussion of the physical basis of active sound control that concentrates on three-dimensional sound fields is presented. >
965 citations
TL;DR: In this article, the authors compared two different formulations for calculating the total acoustic power radiated by a structure, in terms of the amplitudes of the structural modes and the velocities of an array of elemental radiators on the surface of the structure.
Abstract: Two formulations for calculating the total acoustic power radiated by a structure are compared; in terms of the amplitudes of the structural modes and in terms of the velocities of an array of elemental radiators on the surface of the structure. In both cases, the sound radiation due to the vibration of one structural mode or element is dependent on the vibration of other structural modes or elements. Either of these formulations can be used to describe the sound power radiation in terms of a set of velocity distributions on the structure whose sound power radiation is independent of the amplitudes of the other velocity distributions. These velocity distributions are termed ‘‘radiation modes.’’ Examples of the shapes and radiation efficiencies of these radiation modes are discussed in the cases of a baffled beam and a baffled panel. The implications of this formulation for the active control of sound radiation from structures are discussed. In particular, the radiation mode formulation can be used to provide an estimate of the number of independent parameters of the structural response which need to be measured and controlled to give a required attenuation of the radiated sound power.
391 citations
TL;DR: In this article, active control of sound radiation from vibrating plates by oscillating forces applied directly to the structure is analytically studied, and it is shown that global attenuation of broadband radiated sound levels for low to mid-range frequencies can be achieved with one or two control forces, irrespective of whether the system is on or off resonance.
197 citations
TL;DR: In this paper, a series of in-flight experiments on the active contrl of propeller-induced passenger cabin noise in a B.Ae. 748 aircraft were presented. But the results were limited to the first three harmonics of the blade passage frequency.
193 citations