Understanding the aeroacoustics of rotorcraft is valuable to detect and minimize noise sources. However, field studies often lack control over environmental conditions, creating further uncertainty in the rotorcraft's operating parameters. Full-scale experimental studies are also challenging due to the scarcity of large-scale anechoic facilities. Using small-scale model experiments in a pressurized environment can be used to achieve dynamic similarity with the full-scale, thus resolving these challenges. Numerous obstacles remain with collecting aeroacoustic measurements in a pressurized environment, such as quantifying the change in microphone sensitivity with changes in static pressure. This study characterizes a custom-designed pistonphone in atmospheric pressure towards calibrating measurement microphones across a range of static pressures and frequencies.