Two different types of sequences for MLS measurements are available, A or B.
This feature may be used for distortion/non-linearity checking, although it is recommended to use the sine sweep method of measuring harmonic distortion.
Non-linearity causes spurious peaks in the impulse response. The peaks are replications of the true impulse response. For measurements using a different sequence, these peaks are situated at different places in the impulse response. By visually inspecting two impulse responses measured with different sequences, the amount of non-linearity may be determined. Distortion/non-linearity is usually caused by the transducers (either microphone or loudspeaker) and may in some cases be reduced by reducing the volume.