Aspects of MLS Measuring Systems
A maximum-length sequence (MLS) has mathematical properties that make it very useful as an excitation signal for measurement in audio and acoustics. This paper explores the pathology of MLS systems when there is distortion of various kinds. The resulting artefacts can falsify a reverberation plot, reduce the distortion immunity of the measurement system, and give rise to spurious reflections in the impulse response, to name a few negative aspects. On the other hand, MLS systems can also allow the determination of the total distortion of an electroacoustic system when excited by a signal of any desired spectrum, and sensitive tests for determining the presence of distortion are possible due to the time-domain separation of linear and nonlinear components.
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