The basic structure of the system will be:
audio in → anti-aliasing filter → ADC → digital signal processing → output
For the filtering experiments the output will be an analog audio signal (from a DAC); while for the QRSS experiments the output will be a stream of values for plotting in Matlab on a laptop.
The Arduino Due has all that is required for these experiments (ADCs, DACs and a USB serial port).
I will start by writing a simple program to digitise the filtered audio input and pass it directly to the DAC to give an audio signal again.