1. A method for noninvasively estimating a blood pressure, the method comprising: a) extracting a diastolic signal from a phonocardiogram (PCG) signal; b) determining a target interval from the diastolic signal such that the target interval of the diastolic signal includes an S2 component; c) extracting the S2 component from the diastolic signal using the target interval; d) analyzing the extracted S2 component in the target interval to obtain a number of oscillations in the extracted S2 component; e) applying a predetermined relationship between the obtained number of oscillations and blood pressure to generate a blood pressure estimate; and f) displaying the blood pressure estimate.