Rub and Buzz is a term that summarizes all electromechanical problems that can occur on a loudspeaker or loudspeaker driver. There are many different causes, such as rubbing coil, particles in loudspeaker, particles on membrane, air leakage, rattling parts, asymmetric mounting, etc.
Rub & Buzz is best measured with NTi Audios patented PureSound technology, - the industry standard for loudspeaker quality testing.