| 摘要 |
A modal analysis method and apparatus for acoustically determining dynam ic vibration characteristics of a structure, including natural frequencies, mod e shapes and damping factors, is based on a Multiple-Input-Single-Output (MISO ) model. The method and apparatus involve generation of an acoustic excitation signal toward n spatially distributed locations associated with the structur e while the latter is held to allow vibration thereof, one of the locations being chosen as a reference location. A series of microphones are disposed at the locations to produce m complementary sets of n input acoustic pressure-related electrical signals, one of these being chosen as a reference signal associated with the reference location. A Fourier analysis is performed on the sets of input acoustic pressure-related electrical signals to provide corresponding sets of correlated input acoustic pressure-related data in the frequency domain including reference data associated with the reference signal. A vibration transducer such as an accelerometer is used to sense induced output vibration in response to the acoustic excitation at a reference point on the excited structure corresponding to the reference location to produce m complementary sets of output vibration response electrical signals, which are then converted through Fourier analys is into corresponding sets of output vibration response data in the frequency domain. Then, from relations between m corresponding complementary sets of n input transfer functions characterizing the correlation between each set o f input acoustic pressure-related data and the reference data from one hand, a nd m sets of output vibration response data on the other hand, the structural transfer functions characterizing each said set of input acoustic pressure- related data are obtained. Finally, the dynamic vibratory characteristics of the acoustically excited structure are derived from the resulting structural transfer functions through usual calculation techniques.
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