A standard ½” microphone with high sensitivity (50 mV) has a noise floor about 16 dB(A), and the useful measurement range therefore begins at about 19 dB(A). To measure below this level, a special low-noise system is needed.
The 47HC is a prepolarized low-noise microphone set which builds on GRAS' more than 20 years' of experience with state of the art low-noise measurement microphone systems. With this set, the performance previously reserved for externally polarized setups is now available for CCP powered systems.
With a sensitivity of 450 mV/pa and a noise floor at 6.5 dB(A) or lower, it opens up for measurement levels down to about 10 dB(A). Its upper dynamic limit is 100 dB below 8 kHz, 85dB from 8 kHz to 20 kHz