Impulse Response Measurements Using MLS Technique on Nonsynchronous Devices

Maximum-length sequences (MLS) are widely used for measurement of impulse responses of linear time-invariant systems in acoustic and audio systems. It is usually believed that one of the drawbacks of the MLS technique is a requirement on a synchronization of the devices used for the generation and acquisition of the MLS signals. The study presented in this paper shows that the MLS technique can easily be improved and applied to devices that are not synchronous, or even operating at different sampling frequencies. To show the efficiency of the proposed modification to MLS technique we provide several experiments such as a measurement with devices working at 44.1 kHz on the generation side and 96 kHz on the acquisition side, or a measurement of the frequency response function of a cheap mobile phone in which the synchronous clocking would be impossible to realize.