On acoustic in-duct characterization of medium speed IC-engine exhaust system

Antti Hynninen, Mats Åbom

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific


    Predicting and controlling noise from a fluid machine requires a model of the noise sources themselves, i.e., acoustic source data. If the source connects weakly to the surroundings, the standardized free field methods can be used for the source sound power determination, i.e., source characterization. In the duct systems connected to the fluid machines, the acoustic source interacts strongly with the system boundaries and the in-duct source characteristics cannot be described using only the emitted sound power. The following general problems exists: The source characteristics are dependent on the acoustic load and the sound power is reflected from the duct discontinuities as well as from the duct terminations, the sound pressure measurements might be contaminated by the turbulence in the flow, and 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 nonplane wave range is also important. In this paper, methods to determine the in-duct acoustic source data including also the non-plane waves are discussed. The low and high frequency in-duct characteristics of a test engine exhaust system are obtained and combined. The combined source data is useful when designing the components of the exhaust system, for example
    Original languageEnglish
    Title of host publicationProceedings of BNAM 2014
    Place of PublicationTallinn
    PublisherNordic Acoustics Association
    ISBN (Print)978-87-995400-1-3
    Publication statusPublished - 2014
    MoE publication typeB3 Non-refereed article in conference proceedings
    EventBaltic-Nordic Acoustic Meeting, BNAM 2014 - Tallinn, Estonia
    Duration: 2 Jun 20144 Jun 2014


    ConferenceBaltic-Nordic Acoustic Meeting, BNAM 2014
    Abbreviated titleBNAM 2014


    • acoustic source
    • IC-engine
    • exhaust system


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