The design and optimisation of surround sound decoders using heuristic methods

Surround sound has, for a number of years, had the standard of an irregular five-speakers layout (as defined by the ITU), but this is most likely set to expand to 7,9 or more, speaker configurations. The Ambisonic system, pioneered by Micheal Gerzon in the late 1960s, is very well suited to situations where the end system speaker configuration is not fixed in terms of number or position. However, while designing Ambisonic decoders for a regular (e.g. hexagonal) layout is well documented, optimising the decoders for irregular layouts is not a simple task, when optimisation requires the solution of a set of non-linear simultaneous equations [1 – Gerzon & Barton]. This paper describes an alternative approach to the determination of these “optimised coefficients”. This approach, based on a Tabu Search methodology [2 – Berry & Lowndes], efficiently determined sets of alternative optimal settings which were better (in terms of the reviewed parameters) than the results obtained using the standard analytical methods.