A method of operating an apparatus comprising a control unit to determine at least one of a position and an orientation of a wearable device on a subject, the method comprising: acquiring , by the control unit , at least one physiological characteristic signal from a subject, the at least one physiological characteristic signal acquired from the subject having one or more characteristics indicative of at least one of a position and an orientation of a wearable device on the subject; and determining , by the control unit , the at least one of the position and orientation of the wearable device on the subject based on the one or more characteristics indicative of the at least one of the position and orientation of the wearable device on the subj ect, wherein the at least one physiological characteristic signal comprises i) an electrocardiogram signal, wherein the one or more characteristics indicative of the at least one of the position and orientation of the wearable device on the subject comprises one or more of: a morphology of the electrocardiogram signal; an amplitude of the electrocardiogram signal; and a polarity of the electrocardiogram signal; or ii) an acoustic signal, wherein the one or more characteristics of the acoustic signal indicative of the at least one of the position and orientation of the wearable device on the subject comprises one or more of: a frequency of the acoustic signal; a power of the acoustic signal; a phase of the acoustic signal; and a temporal feature of the acoustic signal. acquiring , by the control unit , at least one physiological characteristic signal from a subject, the at least one physiological characteristic signal acquired from the subject having one or more characteristics indicative of at least one of a position and an orientation of a wearable device on the subject; and determining , by the control unit , the at least one of the position and orientation of the wearable device on the subject based on the one or more characteristics indicative of the at least one of the position and orientation of the wearable device on the subj ect, wherein the at least one physiological characteristic signal comprises i) an electrocardiogram signal, wherein the one or more characteristics indicative of the at least one of the position and orientation of the wearable device on the subject comprises one or more of: a morphology of the electrocardiogram signal; an amplitude of the electrocardiogram signal; and a polarity of the electrocardiogram signal; or ii) an acoustic signal, wherein the one or more characteristics of the acoustic signal indicative of the at least one of the position and orientation of the wearable device on the subject comprises one or more of: a frequency of the acoustic signal; a power of the acoustic signal; a phase of the acoustic signal; and a temporal feature of the acoustic signal. i) an electrocardiogram signal, wherein the one or more characteristics indicative of the at least one of the position and orientation of the wearable device on the subject comprises one or more of: a morphology of the electrocardiogram signal; an amplitude of the electrocardiogram signal; and a polarity of the electrocardiogram signal; or a morphology of the electrocardiogram signal; an amplitude of the electrocardiogram signal; and a polarity of the electrocardiogram signal; or ii) an acoustic signal, wherein the one or more characteristics of the acoustic signal indicative of the at least one of the position and orientation of the wearable device on the subject comprises one or more of: a frequency of the acoustic signal; a power of the acoustic signal; a phase of the acoustic signal; and a temporal feature of the acoustic signal. a frequency of the acoustic signal; a power of the acoustic signal; a phase of the acoustic signal; and a temporal feature of the acoustic signal. <EOS>