INSTRUMENT design – DC-blocking filter object
Based in a design from Perry Cook and Gary Scavone’s Synthesis ToolKit (STK), the Odcblock object is a simple one-pole/one-zero filter set to remove a DC (0 Hz) offset component in the output signal. The recursive filter equation used for this object is:
y[n] = x[n] - x[n-1] + 0.99*y[n-1]
where y[n] and y[n-1] are the current and previous outputs of the equation, respectively, and x[n] and x[n-1] are the current and previous sample inputs to the filter equation.
This object is very useful in cases where the output of a signal-processing or synthesis algorithm may not necessarily be symmetrical around 0.0. Many physical-modelling algorithms use this filter.