A signal processing apparatus for determining a heart rate includes a plurality of sensors configured to detect changes in blood properties in a users skin and a heart rate Kalman filter configured to compute a heart rate on the basis of signals obtained from the plurality of sensors. A method of computing a heart rate using the apparatus includes detecting changes in blood properties with a plurality of sensors, and computing with a heart rate Kalman filter the heart rate on the basis of signals obtained from the plurality of sensors.
