管道噪声有源控制的声学特性研究 Ⅰ理论分析

Study on Acoustic Character of Active Noise Attenuation in Ducts I Theoretical Analysis

在假设半无限长管道的前提下,详细分析了噪声有源控制系统作用下的管道声场特性.研究结果表明,当达到理想消声效果时,从次级源到管道下游声场的声压为0,在初级源与次级源之间形成一个声反射系数模等于1的驻波场,在次级源位置的声反射系数为-1,声阻抗为0.这时初级源的辐射声阻抗为一个纯虚数量,它不再向外界辐射声能.

The acoustic character controlled by the active noise attenuation system in ducts has been analyzed in detail on premise of semi-infinite ducts. The studying results have proved that under the ideal noise cancellation condition the reflection coefficient module of standing wave field between the noise source and the secondary source is equal to 1, the reflection coefficient at the secondary source is equal to 1, the acoustic impedance at the position is equal to zero. And the acoustic radiation impedance of noise source is close to a pure imaginary number, namely, it cannot radiate acoustic energy again.