A noise sensor is disposed adjacent a speaker within an ear cup of a hearing protection device. The speaker is disposed within a speaker housing and the noise sensor is disposed within a sensor housing, the sensor housing coupled to the speaker housing such that the noise sensor and speaker remain adjacent one another. The noise sensor includes at least a microphone operably coupled to a printed circuit board. The sensor housing defines an axial bore such that the noise sensor can receive acoustic signals via the axial bore. The sensor housing can be coupled to the speaker housing such that the noise sensor is sealed therebetween and receives acoustic signals via a distal end of the axial bore opposite the speaker. A calibration tool can be disposed to the axial bore via the distal end for airtight calibration of the noise sensor.