ヘテロダインを応用した低サンプリングで実行する狭帯域能動的音響制御

抄録

In conventional active noise control (ANC), the sampling frequency of controller is determined so that the Nyquist frequency is higher than the highest frequency of noise. This setting is not efficient for cost when the noise is narrow band noise. In this case, the sampling frequency can be lowered to control. However, it is necessary to shift the noise frequency below the Nyquist frequency. In this paper, to control narrow band noise, heterodyne is used to shift the frequency of noise. By using heterodyne, frequency band of some signal can be shifted to lower and higher frequency band. To use the lower band in the A/D converter, a low pass filter is placed in the previous stage instead of anti-aliasing filter. On the other hand, in the latter stage of the D/A converter, to use higher frequency band, a high pass filter is placed. This method can be used conventional adaptive algorithm, because it is not adaptive update method but input and output method (in other words, control band choosing method). The validity of the proposed method is shown in numerical simulation and experiment. The results show control effect can be obtained for noise above the Nyquist frequency by proposed method. Moreover, it is shown that band stop performance of high pass filter is dominant for control efficient.