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Procedure to estimate the in-duct sound power in the high frequency range with non-plane waves
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. KTH, School of Industrial Engineering and Management (ITM), Centres, Competence Center for Gas Exchange (CCGEx).ORCID iD: 0000-0001-7898-8643
2012 (English)In: ASME 2012 Noise Control and Acoustics Division Conference at InterNoise 2012, ASME Press, 2012, 181-191 p.Conference paper (Refereed)
Abstract [en]

The acoustic characterization of fluid machines, e.g., internal combustion engines, compressors, or fans is of great importance when designing the connected duct systems and its silencers. For machines connected to large ducts where also the non-plane wave range is important, for instance large diesels and gas turbines, a suitable way to characterize the source is to determine the sound power under reflection free conditions. For the low frequency plane wave range in-duct sound power can be measured with the widely used two microphone method. The goal of this study is to investigate how, starting from the two-microphone approach, a suitable wall mounted microphone configuration can be defined and used to estimate the propagating in-duct sound power also beyond the plane wave range. For this purpose an acoustic source test-rig was built and numerical simulations were also conducted. The in-duct sound power from monopole, dipole, and quadrupole source types was determined using twelve wall mounted microphones and cross-spectra averaging methods. The in-duct results were compared against sound power measured using the reverberation room method (ISO 3741). Based on the simulations and the experimental results the best microphone positions and weighting factors were determined.

Place, publisher, year, edition, pages
ASME Press, 2012. 181-191 p.
Keyword [en]
Acoustic characterization, Acoustic sources, Averaging method, Frequency ranges, Microphone positions, Reverberation rooms, Two-microphone methods, Weighting factors
National Category
Fluid Mechanics and Acoustics
URN: urn:nbn:se:kth:diva-144786DOI: 10.1115/NCAD2012-0531ISI: 000323912200019ScopusID: 2-s2.0-84884857493ISBN: 978-079184532-5OAI: diva2:717886
ASME 2012 Noise Control and Acoustics Division Conference at InterNoise 2012, NCAD 2012; New York City, NY; United States; 19 August 2012 through 22 August 2012

QC 20140519

Available from: 2014-05-19 Created: 2014-04-29 Last updated: 2015-11-19Bibliographically approved
In thesis
1. Acoustic In-duct Characterization of Fluid Machines with Applications to Medium Speed IC-engines
Open this publication in new window or tab >>Acoustic In-duct Characterization of Fluid Machines with Applications to Medium Speed IC-engines
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The unwanted sound, noise, can lead to health problems, e.g. hearing loss and stress-related problems. A pre-knowledge of noise generation by machines is of great importance due to the ever-shorter product development cycles and stricter noise legislation. The noise from a machine radiates to the environment indirectly via the foundation structure and directly via the surrounding fluid. A fluid machine converts the energy from the fluid into mechanical energy or vice versa. Examples of the fluid machines are internal combustion engines (IC-engines), pumps, compressors, and fans. Predicting and controlling noise from a fluid machine requires a model of the noise sources themselves, i.e. acoustic source data. In the duct systems connected to the fluid machines, the acoustic source interacts strongly with the system boundaries, and the source characteristics must be described using in-duct methods.

Above a certain frequency, i.e. first non-plane wave mode cut-on frequency, the sound pressure varies over the duct cross-section and non-plane waves are introduced. For a number of applications, the plane wave range dominates and the non-plane waves can be neglected. But for machines connected to large ducts, the non-plane wave range is also important. In the plane wave range, one-dimensional process simulation software can be used to predict, e.g. for IC-engines, the acoustic in-duct source characteristics. The high frequency phenomena with non-plane waves are so complicated, however, that it is practically impossible to simulate them accurately. Thus, in order to develop methods to estimate the sound produced, experimental studies are also essential.

This thesis investigates the acoustic in-duct source characterization of fluid machines with applications to exhaust noise from medium speed IC-engines.  This corresponds to large engines used for power plants or on ships, for which the non-plane wave range also becomes important. The plane wave source characterization methods are extended into the higher frequency range with non-plane waves. In addition, methods to determine non-plane wave range damping for typical elements in exhaust systems, e.g. after-treatment devices, are discussed.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. xi, 63 p.
TRITA-AVE, ISSN 1651-7660 ; 2015:86
in-duct, acoustic source, source characterization, IC-engine
National Category
Fluid Mechanics and Acoustics
urn:nbn:se:kth:diva-177341 (URN)978-91-7595-765-4 (ISBN)
Public defence
2015-12-10, sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)

QC 20151119

Available from: 2015-11-19 Created: 2015-11-18 Last updated: 2015-12-14Bibliographically approved

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Åbom, Mats.
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