Historically speaking, underwater acoustic vector sensors have seen widespread use in direction finding applications. However, given that this class of sensor typically measures both the acoustic pressure and at least one component of the particle velocity at a single point in space, they can be used effectively to measure the acoustic intensity and/or the acoustic impedance. These metrics can be useful in understanding the acoustic field associated with simple and complex sound radiators. The focus of this paper concerns the development of a uniaxial pressure-acceleration (p-a) probe to measure the specific acoustic impedance of a spherical sound projector (i.e., International Transducers Corporation ITC1001 transducer) over the frequency range from 2.5 to 10 kHz. The design, fabrication, and calibration of the probe are covered along with the results of the aforementioned experiment. Results show that reasonable agreement was obtained between the measured data and an analytical prediction, which models the sound projector as a point source positioned in a free-field.