An implantable medical device system, comprising: a first acoustical sensor adapted to be operatively positioned in a first internal body location to have a first level of responsiveness for sensing heart sounds in a patient, and to generate a first signal responsive to the sensed heart sounds; a second acoustical sensor adapted to be operatively positioned in a second internal body location to have a second level of responsiveness for sensing heart sounds in the patient less than the first level of responsiveness, and to generate a second signal responsive to the heart sounds; and an implantable or subcutaneously positionable medical device comprising a housing and a processor enclosed in the housing, the processor configured to receive the first signal and the second signal and generate a corrected first signal by canceling non-cardiac signals in the first signal using the second signal, wherein the housing comprises: a first major side adapted to be inwardly-facing when implanted and having an internal surface and an external surface, and a second major side adapted to be outwardly-facing when implanted and having an internal surface and an external surface; characterized in that the first acoustical sensor is positioned along one of the internal surface and the external surface of the first major side, and the second acoustical sensor is positioned along one of the internal surface and the external surface of the second major side, wherein the second acoustical sensor) is positioned to be shielded from the patient's heart by the housing and to be less responsive to heart sounds than the first acoustical sensor. a first acoustical sensor adapted to be operatively positioned in a first internal body location to have a first level of responsiveness for sensing heart sounds in a patient, and to generate a first signal responsive to the sensed heart sounds; a second acoustical sensor adapted to be operatively positioned in a second internal body location to have a second level of responsiveness for sensing heart sounds in the patient less than the first level of responsiveness, and to generate a second signal responsive to the heart sounds; and an implantable or subcutaneously positionable medical device comprising a housing and a processor enclosed in the housing, the processor configured to receive the first signal and the second signal and generate a corrected first signal by canceling non-cardiac signals in the first signal using the second signal, wherein the housing comprises: a first major side adapted to be inwardly-facing when implanted and having an internal surface and an external surface, and a second major side adapted to be outwardly-facing when implanted and having an internal surface and an external surface; characterized in that the first acoustical sensor is positioned along one of the internal surface and the external surface of the first major side, and the second acoustical sensor is positioned along one of the internal surface and the external surface of the second major side, wherein the second acoustical sensor) is positioned to be shielded from the patient's heart by the housing and to be less responsive to heart sounds than the first acoustical sensor. a first major side adapted to be inwardly-facing when implanted and having an internal surface and an external surface, and a second major side adapted to be outwardly-facing when implanted and having an internal surface and an external surface; characterized in that the first acoustical sensor is positioned along one of the internal surface and the external surface of the first major side, and the second acoustical sensor is positioned along one of the internal surface and the external surface of the second major side, wherein the second acoustical sensor) is positioned to be shielded from the patient's heart by the housing and to be less responsive to heart sounds than the first acoustical sensor.