This post is mostly for fun and educational purposes. So, there are a lot of common methods in areas of sound and image processing. For example, Fourier, wavelet transforms are used heavily for analysis and compression of both audio and video. In addition, there are a lot of different denoising filters based on the same ideas, etc.
One reason for that (as I think), because sound can be considered as a one-dimensional movie (from processing point of view). If an image is 2D function, mapping brightness (intensity, amplitude) to pixel position then a movie is just a change of this function over time (so it is 3D in the end). With audio it is a bit different.