2pSPb11. Planar acoustic holographic reconstruction by using a moving array.

Session: Tuesday Afternoon, May 14

Time: 4:45

Author: H.-S. Kwon
Author: S.-H. Park
Author: Y.-H. Kim
Location: NOVIC, Dept. of Mech. Eng., KAIST, Taejon 305-701, Korea
Author: B.-S. Ko
Location: Daewoo Motor Co., Inchon, Korea


Planar acoustic holography has been well acknowledged as a useful tool to predict whole sound fields in space. In practical applications, however, an insufficient number of microphones has trouble measuring whole holograms, therefore limiting the improvement to construct a better picture of sound. This problem conveys the issue to virtually increase the number of microphones so that it can construct a better, realistic sound field. As one of these measuring techniques, the conventional scanning technique requires a reference and holds the array during the measurement of pressures. Instead, the proposed method measures the hologram continuously by a moving array without a reference. Its basic idea is that the pressure signal of a moving microphone is modulated with the carrier frequency which is the frequency of the sound field. Although this is a time signal, it includes the spatial information of pressure distribution; i.e., hologram, due to a constant moving speed. The bandwidth of modulated signal is directly proportional to the Mach number, therefore generally narrow, a hologram can be successfully recovered unless there is a closely located frequency; not closer than the bandwidth. Also this technique can be directly applied to the hologram measurement of a moving source with a fixed array. This method is demonstrated by computer simulations and experiments.

from ASA 131st Meeting, Indianapolis, May 1996