Long‐Wavelength Acoustic Holography

On nearfield acoustic holography

Such functions u are called radiating solutions. Pressure measurements are taken by acoustical sensors located in a domain Ω0 inside or outside the cabin or on a surface Γ0 = ∂Ω0 . Our goal is to reconstruct u inside Ω, or the normal velocity v = ∂νu on Γ = ∂Ω, (ν is the unit exterior normal to ∂Ω). This is a mathematical model of the nearfield acoustic holography [W], [Wu]. H(m)(Ω) denotes the...

Near-Field Acoustic Holography: The Frame Drum

A phase-sensitive setup for near-field acoustic holography was established in order to determine the characteristic resonance modes of a vibrating membrane. The experiment was carried out using a frame drum as the vibrating system of interest. By exciting the membrane at certain fundamental frequencies and recording the complex signals from the pressure and particle velocity fields across the d...

Comparison of patch acoustic holography methods for confined space

Localization and characterization of noise and vibration sources through measurement of sound fields radiated from vibrating structures plays an important role in vibration diagnostics. Sound pressure field measured in closed distance to the source with a microphone array is then inversely processed with the suitable near-field acoustic holography method to obtain the estimation of sound field ...

Near field acoustic holography with particle velocity transducers

Field reconstruction by acoustic holography technique based on BEM

This paper presents a technique of surface field reconstruction for nonseparable geometry based on the boundary element method and the singular value decomposition. The sound sources are axisymmetric bodies with arbitrary boundary conditions. The hologram data are got from a cylindrical surface that encircles the source. By the use of axisymmetric property of the body, the two-dimensional integ...