What is Multi-channel Audio?
Multi-channel audio is sound that has more than one source. In home theaters the figures 5.1 and 7.1 mean that a respective audio system has 5 or 7 main speakers plus a subwoofer that plays the LFE (low frequency effect) channel. The number of surround speakers determines the difference between the formats: two in 5.1 and four in 7.1.