Abstract
This study concerns measurement of natural vibration of three-dimensional acoustic space by multi-point excitation using decentralized control. A set of acoustic excitation system consists of a speaker, a microphone, and a local feedback controller. The acoustic excitation system targets the frequency range from 100Hz to 500Hz that often becomes a problem at automobile interior noise. Natural vibration of three-dimensional acoustic space crowds in the narrowband. One-point excitation is a useful technique that can be used to measure natural vibration easily but not suitable for excitation of natural vibration that crowds in the narrowband. Multi -point excitation using centralized control is general technique and it requires different adjustment of each speaker according to modes. Therefore, its control becomes complicated when number of excitation-point is increased and this is the current problem of multi -point excitation technique. In this paper, as a technique that can measure natural vibration of three-dimensional acoustic space easily, proposes multi-point excitation using decentralized control by local feedback control that makes acoustic space into condition of undamped vibration. Natural vibration of three-dimensional acoustic space is measured using the four acoustic excitation systems that is local feedback controlled and input the excitation signal into only one of the four acoustic excitation systems. To reduce effect of acoustic damping by local feedback control, the frequency peak of transfer function is sharpened and some modes that are not able to excited by one-point excitation is definitely excited.
