Heart failure is a major public health problem leading to impaired quality of life, shortness of breath, and high mortality rates. In more than half of the cases, in women even more than in men, the important underlying cause is stiffening of the left ventricular part of the heart muscle, leading to poor filling of the heart. Currently there is no good test to diagnose increased stiffening of the heart and there is no good method of monitoring any therapy. The investigators propose a novel method of diagnosis that is based on safe and noninvasive echographic imaging of the heart. This method aims to measure minute natural vibrations of the heart wall. The research focuses to understanding and interpreting these vibrations to deduce the stiffness of heart wall. Experimental validation in both a laboratory environment and in three hospital centers will show its applicability.