The present application discloses an apparatus for determining a blood pressure of a subject. The apparatus includes one or more sensors configured to measure a first physiological parameter of the subject; a memory; and one or more processors. The memory stores computer-executable instructions for controlling the one or more processors to decompose a first physiological signal corresponding to the first physiological parameter using an empirical mode decomposition algorithm into a sum of a plurality of intrinsic mode functions and a residual; identify one or more first intrinsic mode functions of the plurality of intrinsic mode functions that are associated with a noise signal, thereby obtaining one or more second intrinsic mode functions of the plurality of intrinsic mode functions that are different from the one or more first intrinsic mode functions; and calculate a denoised physiological signal by accumulating the one or more second intrinsic mode functions.