If you want to learn more Digital Signal Processing, go and check out the website I've been running for a few years where I collect all the free online courses, introduction videos, FAQs and textbooks on DSP that you can use to teach yourself:
Yes, I make passive income via Amazon click-throughs. The focus of my website is on music instruments, btw.
Which was an enjoyable primer if you are interested in DSP.
contains links to documents Gilbert Strange and Rick Lyons. These two are much more math-intensive than many of the other introductions.
And if you want to go whole hog, check out the free online lectures:
I really like the first, "Foundations of Signal Processing", as a linear algebra centered treatment of the topic.
1. It's free in PDF by chapter or you can buy it.
2. It has every example in BASIC. Now, BASIC obviously stinks, right? The idea isn't to use the code from the book, but the fact that it's in BASIC means it's been so simplified that you can follow it step-by-step and quickly implement it in your language of choice.