“…The sensor positions used in the primary prevention studies were the ear canal [ 20 , 33 , 38 , 42 , 43 , 72 ], behind the ear [ 35 , 37 ], the concha [ 34 ], the earlobe [ 32 ], the inner ear [ 75 ], and multiple positions [ 36 ]. The sensor positions in the secondary prevention studies were the ear canal [ 21 , 22 , 40 , 44 , 45 , 47 , 50 , 58 , 60 - 65 , 67 , 68 , 71 ], behind the ear [ 51 , 54 - 57 , 59 ], around the ear [ 41 , 66 , 70 ], the earlobe [ 48 , 69 ], and multiple positions [ 39 , 46 , 49 , 52 , 53 , 78 ]. The sensor positions in the tertiary prevention studies were the ear canal [ 18 , 19 , 74 ] and multiple positions [ 76 ].…”