A controller-transmitter transmits acoustic energy through the body to an implanted acoustic receiver-stimulator. The receiver-stimulator converts the acoustic energy into electrical energy and delivers the electrical energy to tissue using an electrode assembly. The receiver-stimulator limits the output voltage delivered to the tissue to a predetermined maximum output voltage. In the presence of interfering acoustic energy sources output voltages are thereby limited prior to being delivered to the tissue. Furthermore, the controller-transmitter estimates the output voltage that is delivered to the tissue by the implanted receiver-stimulator. The controller-transmitter measures a query spike voltage resulting from the electrical energy delivered to the tissue by the receiver-stimulator, and computes a ratio of the predetermined maximum output voltage and a maximum query spike voltage. The maximum query spike voltage is computed by detecting a query spike voltage plateau. Based on this ratio, the controller-transmitter uses a measured query spike voltage to estimate the output voltage delivered by the receiver-stimulator to tissue.
