Heart sound detection systems and methods can use updated heart sound expectation window functions to detect heart sounds. In an example, an initial heart sound expectation window function that describes a heart sound timing can be a function of a physiologic variable such as heart rate, intrinsic vs. non-intrinsic beat, respiration rate, index of circadian timing, or posture. The function can include at least one characteristic parameter that describes a value of the heart sound timing at a specified value of the physiologic variable. In an example, information about a patient heart sound can be detected and used to update a characteristic parameter of an initial heart sound expectation window function, and an updated heart sound expectation window function can be provided using the updated characteristic parameter.
