虚拟声屏障系统中虚拟传感器位置的优化研究

Optimization of the locations of the virtual sensors in the virtual sound barrier system

对于某一特定目标区域,虚拟声屏障系统的误差传感器阵列处于目标区域中某一最优位置,其降噪量最大.然而,误差传感器阵列处于目标区域中会妨碍人头的活动.使用虚拟传感器技术,将虚拟传感器布放于目标区域中,物理传感器布放于目标区域边界,可以解决此问题.前述最优位置即为虚拟传感器的理想最优位置.由于虚拟传感器处声压预测方法的限制,存在一个虚拟传感器的实际最优位置,虚拟传感器布放于实际最优位置时系统性能比布放于理想最优位置时好.控制声源与物理传感器距离较远时,即使虚拟传感器布放于实际最优位置,系统性能与误差传感器处于目标区域边界(不使用虚拟传感器)相比改进不大.然而,控制声源与物理传感器距离较小时,虚拟传感器布放于实际最优位置,与不使用虚拟传感器相比,系统性能提高明显,在550Hz以下低频,系统降噪效果有5dB以上的增加,取得10dB有效降噪静区的上限频率也大幅提高.

In previous works, the error sensors of the virtual sound barrier （VSB） system are positioned at the border of the target region. In practice, the noise reduction in the target region is maximal when error sensors of the VSB system are located at the certain best locations in the target region. However, this sort of arrangement results in the interference of the error sensors to the human head. This problem should be solved by the application of the virtual sensor strategy, in which the virtual sensors are positioned in the target region and the physical sensors are positioned at the border of the target region. The best locations mentioned above are theoretical optimal locations of the virtual sensors. Due to the limitation of the method by which the pressures at virtual sensor locations are estimated, the practical optimal locations of virtual sensors exist. The performance of the VSB system with virtual sensors in practical optimal locations is better than that in theoretical optimal locations. The larger the distance between the virtual sensors and the physical sensors is, the larger the estimation error is and the lower the noise reduction at the virtual sensors is. It will result in the decrease of the noise reduction in the target region. Therefore, the practical optimal locations of virtual sensors are closer to the border than the theoretical optimal locations of virtual sensors. With the larger distance between control sources and physical sensors, the performance of the VSB system with the virtual sensors positioned in practical optimal locations is hardly improved, compared with that of placing the error sensors at the border of the target region without virtual sensors. However, when the distance between control sources and physical sensors is very small, the performance is improved obviously. For the 16--channel cylindrical VSB system introduced in this paper, when the target region is of 0. 2 m height and 0.2 m radius, the noise reduction in the target region increases more than 5 dB in the frequency range of less than 550 Hz and the upper limiting frequency of creating the 10 dB quiet zone is increasing obviously. Therefore, the introduction of the virtual sensors is beneficial to develop a compact VSB system.