数字混响效果器的设计研究

Study on the design of digital reverberation processor

混响效果器的冲激响应常常具有很长的长度,应用目前常规滤波器的设计方法很难在实时处理的条件下使误差、存储量和延迟较小。根据冲激响应的频谱能量基本上集中在低频这一特点,本文提出一种将高低频段分别处理的设计方法。首先对冲激响应和信号的低频段进行抽取,抽取后的冲激响应构成FIR滤波器,抽取后的信号通过这个滤波器后再进行零值内插,然后通过一个低通滤波器输出。冲激响应的高频部分在时间较长时渐趋于零。因而将其截断后再采用变换域处理方法获得信号高频部分的输出。这一方法对于TMS320C5402 DSP芯片来说,能够在使误差、存储量和延迟较小的条件下达到实时处理。

The impulse response of a digital reverberation processor often has a very long length, which makes the real-time processing very difficult with small error, store and delay. This paper proposes to process the high-frequency part and low-frequency part separately. That is, the low-frequency parts of input signal and impulse response are separately decimated with lower sampling rate, the decimated impulse response forms a FIR filter, the decimated low-frequency part of the input signal passes this FIR filter and is then interpolated with zeroes, and then passes a low-pass filter to obtain the output. The energy of the high-frequency part of an impulse response, when time is long, tends to zero. So the high-frequency output can be obtained by cutting it and then using a transform method. For TMS320C5402 DSP, this method can achieve real-time processing with small error, store and delay.