Near field acoustic holography with particle velocity transducers

Near field acoustic holography with particle velocity transducers

Near field acoustic holography based on the equivalent source method and pressure-velocity transducers.

The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has recently been demonstrated. This paper examines whether there might be a similar advantage in using the p...

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...

Statistically optimized near field acoustic holography using an array of pressure-velocity probes.

Statistically optimized near field acoustic holography (SONAH) differs from conventional near field acoustic holography (NAH) by avoiding spatial Fourier transforms; the processing is done directly in the spatial domain. The main advantage of SONAH compared with NAH is that the usual requirement of a measurement aperture that extends well beyond the source can be relaxed. Both NAH and SONAH are...

Near-Field Acoustic Holography of a Vibrating Drum Head

This paper explains the design and construction of a phase-sensitive near-field acoustic holography apparatus. By using phase-sensitive lock-in amplifier techniques to record the complex signals of pressure and particle velocity microphones over an extended spatial region, small vibrations can be imaged using the acoustical properties of said vibrations. The apparatus is tested on a vibrating d...