If a polarized hydrogen or oxygen electrode is irradiated with ultrasonic waves, an alternating component is produced in the electrode potential. This effect is believed to depend primarily on the formation of a gas phase at the surface of the electrode. Indications are that the acoustical sensitivity is a function of the polarizing current and the nature of the electrolytic solution as well as the frequency. Pulse techniques have been used in the investigation of the effect in order to avoid the complications associated with electromagnetic coupling. The response of the polarized hydrogen electrode has been observed to be as large as − 150 db re: one volt per dyne/cm2. Such an effect may find interesting amplications in acoustics, since it can be utilized in the form of virtually a point probe.