A conically shaped piezoelectric probe of ammonium dihydrogen phosphate is described. Its sensitivity over a frequency range from 1235 to 1280 kc was obtained by means of a reciprocity calibration. The average value is about 0.12 microvolt per dyne per square centimeter. Since the measured pattern of the probe as a receiver was the same at various points in the acoustic field, it may be concluded that the probe is a “point source.”