Never say never again.
Time ago Liberty Instrument IMP worked with a single impulse stimulus, with the option to average multiple runs in order to improve the S/N ratio by averaging the ambient noise. Sometimes one of these "averaging" pulses completely messed up the measurement, because this one single pulse had been overloaded by the neighbour's dog barking, or the neighbour himself slamming a door. Then came IMP/M with a MLS (minimum lenght sequence) hardware generator with a much higher stimulus energy and consequently with more robust and better S/N ratio results. And then came the sinesweep method along with capable soundcards, which made MLS/M obsolete.
