A great introduction to digital signal processing, including the maths!
This is an excellent introduction to digital signal processing. It’s a bit too long to assign as anything but an extra reading for Speech Processing, but it you want more details on the Discrete Fourier Transform and digital filters it’s a great place to start
Lyons, Richard G. Understanding Digital Signal Processing. 3rd ed. Prentice Hall, 2011.
Available online through the University of Edinburgh library: link
