Near field acoustic holography with microphones mounted on a rigid sphere

Finn Jacobsen, Guillermo Moreno, Efren Fernandez Grande, Jørgen Hald

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review

    Abstract

    Spherical near field acoustic holography (spherical NAH) is a technique that makes it pos-sible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible scattering. This is potentially very useful for source identification. On the other hand a rigid sphere is somewhat more practical than an open sphere, and it is possible to modify the existing spherical NAH theory so that a similar sound field reconstruction can be made with an array of microphones flush-mounted on a rigid sphere. Rigid spheres with flush-mounted microphones are also used for beamforming, and it is known that they are advantageous compared with open spheres for this application. However, whereas beamforming is a far field technique NAH is a near field technique, and spherical NAH based on a rigid sphere is only valid if it can be assumed that the sphere has a negligible in-fluence on the incident sound field, and this is not necessarily a good assumption when the sphere is very close to a radiating surface. This paper describes the modified spherical NAH theory and examines the matter through simulations and experiments.
    Original languageEnglish
    Title of host publicationInter-noise 2008 : From Silence to Harmony
    Publication date2008
    Publication statusPublished - 2008
    Event37th International Congress and Exposition on Noise Control Engineering - Shanghai, China
    Duration: 26 Oct 200829 Oct 2008
    Conference number: 37

    Conference

    Conference37th International Congress and Exposition on Noise Control Engineering
    Number37
    Country/TerritoryChina
    CityShanghai
    Period26/10/200829/10/2008

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