/diy/ - Do It Yourself

I'm interested in building a muffler for my shopvac, however I want it to be a bit more calculated then thowing a couple of PVC pipes together with some stuffing, I want it to be a reactive muffler. I've downloaded a book on muffler design, however it's a high-level scientific book with content like picrelated.
It wouldn't be too bad since I have a degree in mathematics, however I'm not great with physics and I have a hard time understanding the meaning behind many of the equations in there.
So I seem to need one of the two things:
1. A more entry-level accoustics book that might give me understanding of concepts like particle velocity and pressure perturbation and their connection to sound, etc.
2. A non-scientific book/article with muffler design that has some basic formulas for calculating resonating or interference chambers depending on the noise frequency.
If anyone knows of such books, please recommend them, that would be appreciated.