BJ and Kurt comment on how\u00a0 to create a RMS averaged signal for side-chain dynamics purposes. (among others)<\/p>\n
________[How]________<\/span><\/p>\n If you multiply a signal by itself, using MIO Channel Multiplier, To do the “square” part, you use a Channel Multiplier with both inputs feed by the same signal.<\/p>\n To do stereo, you use the Max primitive, which will pass through the larger signal.<\/p>\n To do the mean part, you can use a Low Pass filter.<\/p>\n _______[Why]________<\/span><\/p>\n the standard definition of mean is<\/p>\n mean = sum (x0, x1, x2 … xn)\/n<\/p>\n That yields the mean, but that would not be useful for a continuously applied process, so the mean used in an RMS detector could be a moving window mean<\/p>\n mean_n = sum(x(n-m), x(n-m+1), … x(n))\/m<\/p>\n This is a FIR filter, with equal coefficients of 1\/m and m taps. So when you use an IIR low pass filter, you are basically measuring the mean value. (The mean value is the DC component of a signal. The lower you set the cutoff of the filter, the closer the output of the filter will be to the mean value). For an RMS detector, you don’t really want the the RMS of the signal for all time. You want an new signal that approximates the “instantaneous” RMS level of the signal.<\/p>\n Square -> LPF -> Square-root gives you that.<\/p>\n Thanks BJ & Kurt<\/p>\n","protected":false},"excerpt":{"rendered":" BJ and Kurt comment on how\u00a0 to create a RMS averaged signal for side-chain dynamics purposes. (among others) ________[How]________ If you multiply a signal by itself, using MIO Channel Multiplier, you get the “Square”. If you put that result through a lowpass, you get a\u00a0 kind of “Mean Square” (an exponential moving average). If you…<\/p>\n
\nyou get the “Square”. If you put that result through a lowpass,
\nyou get a\u00a0 kind of “Mean Square” (an exponential moving average).
\nIf you take the square root of that (using Square Root under Math),
\nyou get the Root Mean Square.You get to choose the time constant for
\nyour averaging by tuning the lowpass. This is essentially an RMS-based envelope extractor.<\/p>\n
\nThis is a type of low-pass filter. This sort of FIR is generally inefficient to simply compute a moving average. You can build an IIR filter that has similar pass-band and stop band characteristics as the FIR, but the phase characteristics will be very different, and the transition band will be very different. But that doesn’t matter that much for a detector filter.<\/p>\n