在此基础上进行了谱分析，得到了该模型的谱密度、互谱密度和双互谱密度。
The spectrum density matrix of the proposed model was constructed and its properties are investigated.
第二章介绍波动方程、声能、声能流密度、声强及度量方法、双传声器互谱声强测量原理。
In chapter two, wave motion equation, sound energy, sound energy flux density, sound intensity and its scaling method and the theorem of two-microphone sound intensity have been introduced.
结果表明，利用等工件转角间隔采样通过互功率谱密度方法可以实现相位差的精确在线测试。
The results show that the phase shift angle can be measured accurately based on the cross-spectrum method with equivalent interval sampling of workpiece rotary angles.
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