Mathematica has powerful capabilities for explicit signal processing with large volumes of data, imported and exported in many formats, and for symbolic analysis of signal processing algorithms using state-of-the-art algebraic methods.
Import,
Export — import and export data in standard formats
ListPlay — play a list of amplitude values as a sound
Fourier,
FourierDCT,
FourierDST — discrete Fourier transforms
ListDeconvolve — restore a convolved signal
ZTransform — symbolic Z transform for constructing filters