Supports causal digital audio filters, both general and cascade 2nd-order. Magnitude and phase responses and the specification of the desired filter are graphically displayed together to facilitate filter design. For cascade filters, the pole/zero pattern on the Z-plane unit circle is also displayed. Applies both general and cascade filters to 16-bit mono PCM wave files of any sample rate, one at a time or in batches. Many of the methods used in the program are adapted from Roman Kuc, "Introduction to Digital Signal Processing".

Cascade filter design is accomplished by graphic placement of poles and zeros on the unit circle using a mouse, or by editing an ASCII text file which specifies the pole/zero pattern. The latter method is useful if greater precision is desired than can be accomplished using the mouse. This method allows the design of filters with any magnitude response, within the limits of the precision of the coefficients (15 significant digits). A general filter can be designed by first designing a cascade filter and then saving it as a general filter coefficient file.

Once a filter has been designed, its coefficients can be saved as an ASCII text file. For cascade filters, the pole/zero pattern can also be saved to an ASCII text file. General or cascade filters can be imported by entering the coefficients or pole/zero pattern into an ASCII text file and loading it into the program. Imported cascade filters can the be saved as general or cascade pole/zero files. However, the program can't save an imported general filter as a cascade filter. Another limitation is that program can't save an imported cascade filter as a pole/zero or general filter unless the first numerator coefficient is equal to 1 for all sections. However, such filters can be applied to wave files.