Controlling Ventilation Noises


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Active Control of Fan Noise


Book Description

This report describes the Active Noise Cancellation (ANC) System designed by General Electric and tested in the NASA Lewis Research Center's (LERC) 48 inch Active Noise Control Fan (ANCF). The goal of this study is to assess the feasibility of using wall mounted secondary acoustic sources and sensors within the duct of a high bypass turbofan aircraft engine for global active noise cancellation of fan tones. The GE ANC system is based on a modal control approach. A known acoustic mode propagating in the fan duct is canceled using an array of flush-mounted compact sound sources. The canceling modal signal is generated by a modal controller. Inputs to the controller are signals from a shaft encoder and from a microphone array which senses the residual acoustic mode in the duct. The key results are that the (6,0) was completely eliminated at the 920 Hz design frequency and substantially reduced elsewhere. The total tone power was reduced 6.8 dB (out of a possible 9.8 dB). Farfield reductions of 15 dB (SPL) were obtained. The (4,0) and (4,1) modes were reduced simultaneously yielding a 15 dB PWL decrease. The results indicate that global attenuation of PWL at the target frequency was obtained in the aft quadrant using an ANC actuator and sensor system totally contained within the duct. The quality of the results depended on precise mode generation. High spillover into spurious modes generated by the ANC actuator array caused less than optimum levels of PWL reduction. The variation in spillover is believed to be due to calibration procedure, but must be confirmed in subsequent tests. Pla, Frederic G. and Hu, Ziqiang and Sutliff, Daniel L. Glenn Research Center...




Fans


Book Description

Fans In a unique approach, this textbook combines the design and construction of centrifugal and axial fans with the problem of their noise generation and its mitigation. Easily applicable methods of fan selection, aerodynamic fan design, and fan noise prediction are compiled, including most of the underlying physical principles. Other features of this book include introductions to numerical and experimental methods, simulation-based optimization techniques for fan design, and psychoacoustic methods for evaluating fan noise. Numerous practical problems illustrate and reinforce the ideas and concepts. Content Fan performance parameters, demand of a plant and fan selection, fan performance characteristics, model laws, flow kinematics, efficiencies - Design methods for centrifugal and axial fans - Mechanisms of fan sound generation, methods for fan sound prediction - Psychoacoustic evaluation of fan noise - Design features of noise reduced fans - Computational fluid dynamics, fan test rigs, simulation-based optimization - Practice problems and solutions. Target group Students of mechanical engineering at colleges and universities Engineers in the industrial fan manufacturing industry, planning engineers for heating, ventilation air conditioning systems and in equipment and plant engineering Author Prof. Dr.-Ing. Thomas Carolus taught fluid mechanics at the Department of Mechanical Engineering at the University of Siegen, Germany, with a focus on fluid machinery. This book is a translation of the original German 4th edition Ventilatoren by Thomas Carolus, published by Springer Fachmedien Wiesbaden GmbH, part of Springer Nature in 2020. The translation was done with the help of artificial intelligence (machine translation by the service DeepL.com), but with a subsequent human revision in terms of content. Springer Nature works continuously to further develop tools for the production of books and on the related technologies to support the authors.







Axial Fan Noise Reduction


Book Description

This report contains a survey of Russian technical literature concerning design methodologies for low-noise axial flow fans. Recommendations are cited for nominating the main design parameters, such as rotor and stator blades number combinations, blade shape and tilt, and axial clearance. Comparisons are made with corresponding American sources.--Abstract.




Handbook of Noise and Vibration Control


Book Description

Two of the most acclaimed reference works in the area of acoustics in recent years have been our Encyclopedia of Acoustics, 4 Volume set and the Handbook of Acoustics spin-off. These works, edited by Malcolm Crocker, positioned Wiley as a major player in the acoustics reference market. With our recently published revision of Beranek & Ver's Noise and Vibration Control Engineering, Wiley is a highly respected name in the acoustics business. Crocker's new handbook covers an area of great importance to engineers and designers. Noise and vibration control is one largest areas of application of the acoustics topics covered in the successful encyclopedia and handbook. It is also an area that has been under-published in recent years. Crocker has positioned this reference to cover the gamut of topics while focusing more on the applications to industrial needs. In this way the book will become the best single source of need-to-know information for the professional markets.