Methods and apparatus for noninvasively estimating a blood pressure are provided. A bandpass filter is applied to a second heart sound (S2) component to generate a filtered S2 component. The bandpass filter has a lower cutoff frequency greater than a maximum frequency of the S2 component. The maximum frequency of the S2 component is estimated using the filtered S2 component, a predetermined relationship is applied between the estimated maximum frequency and blood pressure to generate a blood pressure estimate and the blood pressure estimate is displayed.
