Is DSP a branch of Computational Science? The way I understand it, computational science covers a wide range of fields, all of which use computers and mathematical models to solve a problem involving one of the sciences (physical, life etc.). 

But is DSP, which does use maths to manipulate a signal, a form of computational science?
Nope. Its not . Although , computational sciences covers very wide range of subjects but to be able to implement DSP , one must have a thorough understanding of signal fundamentals . That is not a part of computational sciences .