I want to start learning about audio signal processing but I cannot find a good starting point. Please suggest books or lecture series.
If you can get it:
might have to buy them used.
is your interest music processing and synthesis?
there are some nice online books. Look for anything Julius Smith. But there are others, but i can't remember any names to search for.
another old one:
My personal favorite, though I don't usually do much audio signal processing, are Julius O. Smith III's Spectral Audio Signal Processing and Physical Audio Signal Processing. They're available online here and here.
A while ago, he made the Physical book available in paperback on Amazon.
Many years ago, when I was studying audio DSP in my university, I had to read the following:
Y. You, “Audio Coding: Theory and Applications,” Springer, 2010 here
A. Spanias, T. Painter, V. Atti, “Audio Signal Processing and Coding,” Wiley, 2007 here.
I was very dissapointed by both. Spanias & Painter provide a nice and thorough overview of MP3 coding (but it contains many typos) though. After a couple of years, I read the books by J. O. Smith III, also mentioned by @Peter K. These are indeed excellent textbooks.