  The task of heart rate estimation using photoplethysmographic (PPG) signal is
challenging due to the presence of various motion artifacts in the recorded
signals. In this paper, a fast algorithm for heart rate estimation based on
modified SPEctral subtraction scheme utilizing Composite Motion Artifacts
Reference generation (SPECMAR) is proposed using two-channel PPG and three-axis
accelerometer signals. First, the preliminary noise reduction is obtained by
filtering unwanted frequency components from the recorded signals. Next, a
composite motion artifacts reference generation method is developed to be
employed in the proposed SPECMAR algorithm for motion artifacts reduction. The
heart rate is then computed from the noise and motion artifacts reduced PPG
signal. Finally, a heart rate tracking algorithm is proposed considering
neighboring estimates. The performance of the SPECMAR algorithm has been tested
on publicly available PPG database. The average heart rate estimation error is
found to be 2.09 BPM on 23 recordings. The Pearson correlation is 0.9907. Due
to low computational complexity, the method is faster than the comparing
methods. The low estimation error, smooth and fast heart rate tracking makes
SPECMAR an ideal choice to be implemented in wearable devices.
