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1.
M. Azarpeyvand 《Acoustical Physics》2008,54(1):1-12
This paper follows up on an earlier paper of the author [1] dealing with the issue of multi-scattering in a typical active
noise control system. This work concerns the effects of the presence of a neighboring wall on the performance of an active
noise cancellation system when the dimension of sources is added to the analysis. Effect of the adjacent wall is taken into
account using the image method, and multi-scattering is also allowed for by the spherical harmonic addition theorem. The recognized
method of separation of variables and appropriate wave field expansions in spherical coordination are used to derive the required
analytical solutions. A primary spherical source radiates at different modes, and a secondary source is modeled as a radially
vibrating cap which resembles a real sound speaker. Our particular interest in this work is to investigate effects of multi-scattering
at intermediate working frequencies of ANC, e.g., about 100–500 Hz. In addition to emphasizing the importance of multi-scattering,
this work endeavors to find the appropriate cap angle of the control source to achieve acceptable noise attenuation for different
vibrating modes of the primary source (monopole, dipole). Numerical results reveal that the presence of a rigid wall will
considerably change the adequate velocity of the secondary source and also show that using a baffled spherical piston instead
of a monopole control source will obviously improve the sound minimization efficiency when the primary source vibrates in
the n = 1 mode in a low frequency range.
Published in Russian in Akusticheskiĭ Zhurnal, 2008, Vol. 54, No. 1, pp. 5–17.
The text was submitted by the author in English. 相似文献
2.
Marek Pawe?czyk 《Applied Acoustics》2002,63(11):1193-1213
The aim of this article is to present in details all the stages of an analogue active noise control system. As the exemplary plant, an active personal hearing protection device is considered. In the introductory section the plant is presented and the state of the art is reported. In subsequent section, first a way of identification of a continuous-time model of the plant is described and performance limitations are analysed. Then, the procedure for designing optimal controller is proposed. It starts from analysing properties of the plant and choosing a suitable controller structure. Next, coefficients of the controller are found following the design premises. These coefficients serve as initial parameters in the optimisation process. For this process the performance index and appropriate constraints are built. Next, details on implementation of the controller using a chip with switched capacitors are given. Attenuation results of various noises are presented. Finally, cost of the hardware is evaluated.The methodology presented in this article can be considered as a detailed procedure for designing and practically realising cheap and easily tuneable controllers providing good noise attenuation and satisfying several constraints related to frequency band, stability margin, etc. 相似文献
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Yuan J 《The Journal of the Acoustical Society of America》2003,114(1):210-217
A robust active noise controller (ANC) is proposed here for finite ducts. While the H(infinity) control theory provides theoretical ground and numerical algorithms to design robust controllers, it is important for an engineer to design and formulate a robust controller so that the objective is more achievable and the H(infinity) constraints less restrictive without sacrificing robustness. A new robust ANC is designed this way with an extra actuator to improve achievable performance and introduce more degrees of freedom to controller parameters. The new strategy relaxes H(infinity) constraints without sacrificing robustness and enables the ANC to tolerate a wide variety of errors and uncertainties including truncation errors between a finite model and an infinite field. Theoretical analysis, numerical examples, and experimental results are presented to demonstrate the improved performance of the proposed ANC when subject to a certain level of uncertainties in a duct. 相似文献
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R.D. Ford 《Journal of sound and vibration》1984,92(3):411-417
Active attenuation of noise in a duct generally requires either one or two rings of cancelling loudspeakers located around the duct perimeter. Consideration is given to the acoustic loading on the loudspeakers and it is shown that the use of a horn is likely to create more problems that it solves. Direct radiator operation, with the drive units attached directly to the duct walls, is preferable. The single ring (monopole) system reflects the noise giving rise to upstream standing waves, meaning that the loudspeakers and amplifiers must be able to handle correspondingly larger signals. The double ring (dipole) system absorbs the noise and is more efficient than the monopole system. The dipole system can be made still more efficient over a narrow band of frequencies by tuning both the loudspeakers and the spacing between them. 相似文献
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Jing Yuan 《Applied Acoustics》2007,68(1):86-96
Feedforward controllers are used in many active noise control (ANC) systems to generate destructive interference in noise fields. An ideal feedforward ANC controller should have an infinite impulse response (IIR) transfer function, but most available feedforward ANC controllers have finite impulse responses (FIR) instead. The main reason is related to the adaptation algorithms of ANC systems. In general, adaptive FIR filters converge faster with guaranteed stability. In this study, the adaptive Laguerre filter is proposed and tested in an ANC application with positive experimental effects. The new ANC controller is an IIR filter, but its adaptation is similar to that of a FIR filter with fast convergence and guaranteed stability. Detailed explanations and analysis are presented in the main text. 相似文献
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This study focuses on robust active control of broadband noise in finite ducts. Our analytical and experimental studies suggest the existence of several technical flaws in the path models of conventional active noise control (ANC) systems. These are sensitivity of the path model with respect to boundary conditions, and nonminimum phase (NMP) secondary and reference paths. For finite ducts with small cross sections, the traveling wave model (TWM) may be adopted to find an effective solution to these problems and lead to a robust ANC system. Since many practical "noisy" ducts are finite with small cross sections, the proposed ANC has many practical applications. Its robustness and ability to suppress broadband noise will be explained theoretically and verified experimentally. 相似文献
14.
A. A. Mal’tsev R. O. Maslennikov A. V. Khoryaev V. V. Cherepennikov 《Acoustical Physics》2005,51(2):195-208
A review of research concerned with adaptive noise and vibration control systems and performed under the supervision of Corresponding Member of the Russian Academy of Sciences V.A. Zverev at Nizhni Novgorod State University in the 1980s and 1990s is presented. The history of the subject is briefly outlined, and the theoretical foundations of the design of adaptive active control systems for random wave fields are considered. The main experimental studies performed in this area of research at the Department of Bionics and Statistical Radiophysics of Nizhni Novgorod State University are described. Promising lines of research in this area are indicated, and examples of the practical application of adaptive control systems are given. 相似文献
15.
Lim H Utyuzhnikov SV Lam YW Turan A 《The Journal of the Acoustical Society of America》2011,129(2):717-725
This paper describes an active sound control methodology based on difference potentials. The main feature of this methodology is its ability to automatically preserve "wanted" sound within a domain while cancelling "unwanted" noise from outside the domain. This method of preservation of the wanted sounds by active shielding control is demonstrated with various broadband and realistic sound sources such as human voice and music in multiple domains in a one-dimensional enclosure. Unlike many other conventional active control methods, the proposed approach does not require the explicit characterization of the wanted sound to be preserved. The controls are designed based on the measurements of the total field on the boundaries of the shielded domain only, which is allowed to be multiply connected. The method is tested in a variety of experimental cases. The typical attenuation of the unwanted noise is found to be about 20 dB over a large area of the shielded domain and the original wanted sound field is preserved with errors of around 1 dB and below through a broad frequency range up to 1 kHz. 相似文献
16.
The feedback active noise control (ANC) can be seen as a predictor, the conventional method based on filtered-x least mean square (FXLMS) algorithm can only be useful for linear and tonal noise, but for nonlinear and broadband noise, it is useless. The feedback ANC using functional link artificial neural networks (FLANN) based on filtered-s least mean square (FSLMS) algorithm can reduce some nonlinear noise such as chaotic noise, but the noise cancellation performance is not very well, at the same time, it is not useful to random noise. To solve the problem above, a new feedback ANC using wavelet packet FXLMS (WPFXLMS) algorithm is proposed in this paper. By decomposing the broadband noise into several band-limited parts which are predictable and each part is controlled independently, the proposed algorithm can not only suppress the chaotic noise, but also mitigate the random noise. Compared with FXLMS and FSLMS algorithms, proposed WPFXLMS algorithm also holds the best performance on noise cancellation. Numerous simulations are conducted to demonstrate the effectiveness of the proposed WPFXLMS algorithm. 相似文献
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This paper deals with the global reduction of axial flow fan noise in ducts in a building using a hybrid passive-active noise control method. The effectiveness of using an infra-red device as a reference signal source is also investigated. It is shown that using such a hybrid noise control system over an axial-flow fan reduces the overall sound pressure level by 5 dB(A) in the surrounding environment and global control of the blade passing frequency can also be achieved. This paper also shows that using an infra-red device as a reference signal source produces marginally better control as compared with using a microphone reference sensor. Moreover, long term stability is guaranteed and the possibility of acoustic feedback is eliminated. 相似文献
18.
C.F. Ross 《Journal of sound and vibration》1978,61(4):473-480
This paper describes an experiment which demonstrates how a useful degree of active noise control can be achieved with ordinary sound amplification and reproduction equipment. A loudspeaker positioned next to a large pair of noisy electricity transformers was made to mimic their noise but in antiphase. The aim of the study was to investigate the degree to which the “antisound” would cancel a disturbing noise heard in a nearby office. Some 20 decibels of control was achieved very easily for the 100 Hz component of the noise but the higher frequency sound could only be controlled in localized patches. The experiment suggests that sounds of discrete frequencies of less than 100 Hz are relatively easily controlled with unsophisticated audio equipment, but that useful control of higher frequency elements is much more difficult. 相似文献
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Active noise control (ANC) systems employing adaptive filters suffer from stability issues in the presence of impulsive noise. New impulsive noise control algorithms based on filtered-x recursive least square (FxRLS) algorithm are presented. The FxRLS algorithm gives better convergence than the filtered-x least mean square (FxLMS) algorithm and its variants but lacks robustness in the presence of high impulsive noise. In order to improve the robustness of FxRLS algorithm for ANC of impulsive noise, two modifications are suggested. First proposed modification clips the reference and error signals while, the second modification incorporates energy of the error signal in the gain of FxRLS (MGFxRLS) algorithm. The results demonstrate improved stability and robustness of proposed modifications in the FxRLS algorithm. However, another limitation associated with the FxRLS algorithm is its computationally complex nature. In order to reduce the computational load, a hybrid algorithm based on proposed MGFxRLS and normalized step size FxLMS (NSS-FXLMS) is also developed in this paper. The proposed hybrid algorithm combines the stability of NSS-FxLMS algorithm with the fast convergence speed of the proposed MGFxRLS algorithm. The results of the proposed hybrid algorithm prove that its convergence speed is faster than that of NSS-FxLMS algorithm with computational complexity lesser than that of FxRLS algorithm. 相似文献
20.
Mohammad JI Elliott SJ Mackay A 《The Journal of the Acoustical Society of America》2008,123(4):1838-1841
This letter investigates the effectiveness of various configurations of reference sensors for feedforward active control systems in vehicles using unconstrained frequency domain optimization. The results from a model problem are based on a fully coupled analysis between the vibration of a car panel and an enclosed acoustic field. These suggest that with correct locations, only a small number of microphones or accelerometers are needed to give good overall performance, despite many uncorrelated primary disturbances being present. Similar results are predicted from road test data. 相似文献