“…One approach is to use a single accelerometer to detect one type of SMM, such as hand flapping when a sensor is worn on the wrist (Gonçalves et al, 2012a ; Rodrigues et al, 2013 ). The second approach is to use multiple accelerometers to detect multiple SMM, such as hand flapping from sensors worn on the wrist, and body rocking with a sensor worn on the torso (Min et al, 2009 ; Min and Tewfik, 2010a , b , 2011 ; Min, 2014 ). Other studies have done the same, but included a detection class where hand flapping and body rocking occur simultaneously in time (i.e., “flap-rock,” see Albinali et al, 2009 , 2012 ; Goodwin et al, 2011 , 2014 ).…”