Glossary definition of 'Maximum Length Sequence'(MLS) A pseudo-random binary sequence which includes all the possible binary combinations of a digital word of length n except all zeros. The sequence itself is then 2n -1 bits long. Maximum Length Sequences have an inherently white (flat) frequency spectrum. They have been used for a number of years for deriving impulse responses by the use of the Fast Hadamard Transform (FHT). The FFT analysis of the resulting impulse response allows quasi-anechoic acoustic measurements. Their use has been largely superseded by Log Swept Sine techniques which have a number of practical advantages.