Real time sound field visualization in the near field, far field and at absorbing surfaces

Abstract

The Microflown is a small sensor that is capable of measuring the acoustic particle velocity. In combination with a small pressure microphone it is possible to measure the complete sound field. If the sound field close to an acoustic material is measured it make sense to measure the particle velocity normal to the surface and the sound pressure. With this, the acoustic impedance and absorption can be measured in real time, and with a high spatial resolution. If the sound field of a sound radiating object is measured, the sound field can be obtained directly. Three applications include: direct acoustic camera, that is the real time display of the sound field (velocity, pressure, intensity). Holography that is the pressure, velocity reconstruction on the surface based on the measured sound field (and other places). And cabin interior noise mapping, that is the visualization of the interior noise perceived on a certain location. With three dimensional sound probes (sound pressure and particle velocity in three dimensions), sources in the free field can be found for both bearings as distance. Most recent developments are presented.