[LAD] Audio problem for numerical optimization

Hi! I'm currently taking a course in University called "How to write fast numerical code". We are to do a group project of 3 persons where we choose a numerical algorithm and optimize it over the course for a particular processor (e.g. apply vectorization, cache optimization etc...). I was wondering if there is an interesting algorithm in audio processing that we could apply. In particular, if there is any library developer out here that would be interested in an optimization of one of the algorithms used, we would be happy to contribute. Ideally, the problem is compute intensive (i.e. bottleneck of algorithm is not the memory hierarchy). FFT is used as an example in the lecture so it cannot be used, unless there is a significant additional computation involved. Thanks very much for suggestions, Jeremia