Download or read book Active Noise Control of Multiple Acoustic Modes in a Circular Duct written by B. J. Ikelheimer and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Modal Concept for Active Noise Control in Circular Or Annular Ducts written by Ulf Tapken and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active control of sound propagation in ducts plays an important role in many technical applications e.g. the attenuation of noise in ventilating system or in the exhaust system of combustion engines. Today many control strategies exist for the simplest case, which is the noise control in the low frequency range in ducts the lateral dimensions of which are small compared to wavelength of sound. Up to the cut-on frequency of the first higher order mode a suppression of the propagating plane sound waves is possible in a broad frequency range. The situation is more difficult when the lateral duct dimensions become large compared to the wavelength as for example in the intake section of an aircraft engine With increasing rotor speed an increasing number of acoustical modes becomes present. This means. the system comprises all increasing number of degrees of freedom. As a consequence. control of the sound field is practicable just in a narrow frequency band or even limited to discrete frequencies.
Download or read book Part I Effects of Diameter on Active Noise Control in Rectangular and Round Ducts written by and published by . This book was released on 2006 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active noise control (ANC) is particularly useful in hard-walled ducts where plane waves propagate. Higher order mode waves are much more difficult to control. Basic acoustic principles dictate that tile cut-on frequency at which higher order modes will first begin to eclipse simple plane waves in a duct will be determined by the cross-sectional diameter of the duct. The lowest frequency for higher order modes will increase as duct diameter decreases. Therefore, the range of frequencies where plane waves dominate will be greater and effective control using ANC better as duct diameter decreases. The result is that somewhat higher frequencies can be controlled with ANC for smaller diameters. Below the first higher order mode cut-on frequency for the largest size studied, there should be little difference in ANC effectiveness between the duct sizes. To test those suppositions, a commercially-available ANC system was used to reduce random noise in rectangular and round ducts having different diameters. Results showed that insertion loss (IL) ranged from S to 30 dB in frequencies ranging from 40-1000 Hz, and varied inversely with size as expected. There was no difference in IL below 280 Hz (p=0.7751) between the different diameter ducts. There was a significant difference between duct diameters above 280 Hz (p
Download or read book New Acoustics Selected Topics written by Carlos Ranz Guerra and published by Editorial CSIC - CSIC Press. This book was released on 2002 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advanced Applications in Acoustics Noise and Vibration written by Frank Fahy and published by CRC Press. This book was released on 2004-07-08 with total page 666 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Applications in Acoustics, Noise and Vibration provides comprehensive and up-to-date overviews of knowledge, applications and research activities in a range of topics that are of current interest in the practice of engineering acoustics and vibration technology. The thirteen chapters are grouped into four parts: signal processing, acoustic modelling, environmental and industrial acoustics, and vibration. Following on from its companion volume Fundamentals of Noise and Vibration this book is based partly on material covered in a selection of elective modules in the second semester of the Masters programme in 'Sound and Vibration Studies' of the Institute of Sound and Vibration Research at the University of Southampton, UK and partly on material presented in the annual ISVR short course 'Advanced Course in Acoustics, Noise and Vibration'.
Download or read book Handbook of Noise and Vibration Control written by Malcolm J. Crocker and published by John Wiley & Sons. This book was released on 2007-10-05 with total page 1594 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book The Active Noise Control of a One dimensional Duct written by Young-Su Lee and published by . This book was released on 1997 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effects of Diameter and Cross sectional Partitioning on Active Noise Control in Round Ducts written by Jeremy Michael Slagley and published by . This book was released on 2006 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active noise control (ANC) is particularly useful in hard-walled ducts where plane waves propagate. Higher order mode waves are much more difficult to control. Basic acoustic principles dictate that the cut-on frequency at which higher order modes will first begin to eclipse simple plane waves in a duct will be determined by the cross-sectional diameter of the duct. The lowest frequency for higher order modes will increase as duct diameter decreases. Therefore, the range of frequencies where plane waves dominate will be greater and effective control using ANC better as duct diameter decreases. The result is that somewhat higher frequencies can be controlled with ANC for smaller diameters. To test those suppositions, a commercially-available ANC system was used to reduce random noise in round ducts having five different diameters. Results showed that insertion loss (IL) ranged from 5 to 30 dB in frequencies ranging from 40--1000 Hz, and varied inversely with size as expected. The same tests were conducted on a rectangular duct with one cross-sectional dimension fixed and one varied at seven different sizes. Results showed similar IL from 5 to 30 dB that varied inversely with size. If smaller diameters have broader frequency ranges that can be controlled with ANC, perhaps one could extend the frequency range for a large cross-section by partitioning it into smaller cross-sections. This hypothesis was tested by two methods of cross-sectional partitioning. Partitioning was achieved in one design by inserting a smaller duct inside a large duct. In a second design, a cross-shaped partition was inserted inside the large duct. ANC IL results were 1.7 to 2 dB better for the large duct partitioned by a smaller inner duct than the large duct alone (p=0.0146 for low frequency and p=0.0333 for high frequency). ANC insertion loss was 5.8 dB better for the large duct partitioned by a cross-shaped splitter at high frequencies than the large duct alone (p=0.0003). However, the cross-shaped partition system was 5.6 dB less effective at low frequencies than the large duct ANC IL alone (p
Download or read book Global Active Noise Control of a One dimensional Acoustic Duct Using a Feedback Controller written by Andrew James Hull and published by . This book was released on 1990 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Noise and Vibration written by Colin Hansen and published by CRC Press. This book was released on 2012-11-02 with total page 1564 pages. Available in PDF, EPUB and Kindle. Book excerpt: Integrating active control of both sound and vibration, this comprehensive two-volume set combines coverage of fundamental principles with the most recent theoretical and practical developments. The authors explain how to design and implement successful active control systems in practice and detail the pitfalls one must avoid to ensure a reliable and stable system. Extensively revised, updated, and expanded throughout, the second edition reflects the advances that have been made in algorithms, DSP hardware, and applications since the publication of the first edition.
Download or read book Noise Control Engineering Journal written by and published by . This book was released on 2002 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-10-22 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational method to predict modal reflection coefficients in cylindrical ducts has been developed based on the work of Homicz, Lordi, and Rehm, which uses the Wiener-Hopf method to account for the boundary conditions at the termination of a thin cylindrical pipe. The purpose of this study is to develop a computational routine to predict the reflection coefficients of higher order acoustic modes impinging on the unflanged termination of a cylindrical duct. This effort was conducted wider Task Order 5 of the NASA Lewis LET Program, Active Noise Control of aircraft Engines: Feasibility Study, and will be used as part of the development of an integrated source noise, acoustic propagation, ANC actuator coupling, and control system algorithm simulation. The reflection coefficient prediction will be incorporated into an existing cylindrical duct modal analysis to account for the reflection of modes from the duct termination. This will provide a more accurate, rapid computation design tool for evaluating the effect of reflected waves on active noise control systems mounted in the duct, as well as providing a tool for the design of acoustic treatment in inlet ducts. As an active noise control system design tool, the method can be used preliminary to more accurate but more numerically intensive acoustic propagation models such as finite element methods. The resulting computer program has been shown to give reasonable results, some examples of which are presented. Reliable data to use for comparison is scarce, so complete checkout is difficult, and further checkout is needed over a wider range of system parameters. In future efforts the method will be adapted as a subroutine to the GEAE segmented cylindrical duct modal analysis program. Kraft, R. E. Unspecified Center NAS3-26617; RTOP 538-03-11...
Download or read book Active Control of Fan Noise written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-30 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational method to predict modal reflection coefficients in cylindrical ducts has been developed based on the work of Homicz, Lordi, and Rehm, which uses the Wiener-Hopf method to account for the boundary conditions at the termination of a thin cylindrical pipe. The purpose of this study is to develop a computational routine to predict the reflection coefficients of higher order acoustic modes impinging on the unflanged termination of a cylindrical duct. This effort was conducted wider Task Order 5 of the NASA Lewis LET Program, Active Noise Control of aircraft Engines: Feasibility Study, and will be used as part of the development of an integrated source noise, acoustic propagation, ANC actuator coupling, and control system algorithm simulation. The reflection coefficient prediction will be incorporated into an existing cylindrical duct modal analysis to account for the reflection of modes from the duct termination. This will provide a more accurate, rapid computation design tool for evaluating the effect of reflected waves on active noise control systems mounted in the duct, as well as providing a tool for the design of acoustic treatment in inlet ducts. As an active noise control system design tool, the method can be used preliminary to more accurate but more numerically intensive acoustic propagation models such as finite element methods. The resulting computer program has been shown to give reasonable results, some examples of which are presented. Reliable data to use for comparison is scarce, so complete checkout is difficult, and further checkout is needed over a wider range of system parameters. In future efforts the method will be adapted as a subroutine to the GEAE segmented cylindrical duct modal analysis program. Kraft, R. E. Unspecified Center NAS3-26617; RTOP 538-03-11...
Download or read book Part II Effects of Cross Sectional Partitioning on Active Noise Control in Round Ducts written by and published by . This book was released on 2006 with total page 37 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active noise control (ANC) is particularly useful in hard-walled ducts where plane waves propagate. Higher order mode waves are much more difficult to control Basic acoustic principles dictate that the cut-on frequency at which higher order modes will first begin to eclipse simple plane waves in a duct will be determined by the cross-sectional diameter of the duct. The lowest frequency for higher order modes will increase as duct diameter decreases. Therefore, the range of frequencies where plane waves dominate will be greater and effective control using ANC better as duct diameter decreases. The result is that somewhat higher frequencies can be controlled with ANC for smaller diameters. If smaller diameters have broader frequency ranges that can be controlled with ANC, perhaps one could extend the frequency range for a large cross-section by partitioning it into smaller cross- sections. This hypothesis was tested by two methods of cross-sectional partitioning. Partitioning was achieved in one design by inserting a smaller duct inside a large duct. In a second design, a cross-shaped partition was inserted inside the large duct. ANC IL results were 1.7 to 2 dB better for the large duct partitioned by a smaller inner duct than the large duct alone (p=0.0146 for low frequency and p=0.0333 for high frequency). ANC insertion loss was 5.8 dB better for the large duct partitioned by a cross-shaped splitter at high frequencies than the large duct alone (p=0.0003). However, the cross-shaped partition system was 5.6 dB less effective at low frequencies than the large duct ANC IL alone (p
Download or read book The Finding Guide to AIAA Meeting Papers written by American Institute of Aeronautics and Astronautics. Technical Information Service and published by . This book was released on 1996 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acoustic Theory of Axisymmetric Multisectioned Ducts written by W. E. Zorumski and published by . This book was released on 1974 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Equations are developed for the acoustic field in a duct system which is made up of a number of connected circular and annular ducts. These equations are suitable for finding the acoustic field inside of and radiated from an aircraft turbofan engine. Acoustic modes are used as generalized coordinates in order to develop a set of matrix equations for the acoustic field. Equations for these modes are given for circular and annular ducts with uniform flow. Modal source equations are derived for point acoustic sources. General equations for mode transmission and reflection are developed and detailed equations are derived for ducts with multiple sections of acoustic treatment and for ducts with circumferential splitter rings. The general theory is applied to the special case of a uniform area circular duct with multisection liners and it is shown that the mode reflection effects are proportional to differences of the acoustic admittances of adjacent liners. A numerical example is given which shows that multisection liners may provide greater noise suppression than uniform liners.
Download or read book Duct Acoustics written by Erkan Dokumacı and published by Cambridge University Press. This book was released on 2021-05-13 with total page 607 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understand topics ranging from the foundations of duct acoustics to acoustic design of mufflers and silencers with this hands-on reference.
