Physiological signal processing is the acquisition, filtering and feature extraction of biological signals, such as heart rate, galvanic skin response, EEG or respiration, to infer a person’s internal physiological or affective state. It combines digital signal processing techniques with domain-specific artefact removal, since biosignals are typically low-amplitude and prone to motion and electrical noise. It is a core input stage for affective computing systems that infer emotion or stress from bodily signals.