A MEMS speaker device including a membrane that forms a first capacitor and a second capacitor, respectively, with a top plate and with a bottom plate. The device includes a driving circuit that operates, during a first operating period, to move the membrane into a first position, in which the membrane is close to the bottom plate, and during a second operating period, to move the membrane into a second position, in which the membrane is close to the top plate. The device includes a testing circuit having a measuring circuit, which generates a first signal, based on a capacitance of one of the first capacitor and the second capacitor and a second signal based on a capacitance of one of the first capacitor and the second capacitor; and a comparator, which compares the first and second signals with at least one first electrical reference quantity.