Precautions for Calibration of Noise Meters
1) Reference sound pressure level: 94dB
2) Reference incident direction: axial direction of the microphone
3) Microphone reference point: the center of the microphone diaphragm.
4) Correction data from sound pressure response to free field response (reference incident direction).
Frequency (Hz) 1k 1.25k 1.6k 2k 2.5k 3.15k
Correction value dB 0.2 0.3 0.4 0.5 0.6 0.8
Frequency (Hz) 4k 5k 6.3k 8k 10k 12.5
Correction value dB 0.2 0.3 0.4 0.5 4.5 6.2
5) Electrical input equipment: Equivalent impedance can be used to replace the microphone for electrical signal testing. The capacitance of the equivalent impedance is 20pF, and the insulation resistance is greater than 1G Ω. When using, rotate the shielding cylinder with equivalent impedance onto the preamplifier.
6) Maximum background noise: When the sound level meter is placed in a low sound level field and the microphone is replaced with the above matching device and short-circuited, the possible high local noise is 23dB (electrical noise level is 23dB).
7) Maximum allowable sound pressure level on the microphone: 145dB
8) Maximum peak input voltage of electrical input equipment: 10 Vp-p
9) When the sound level meter meets the technical requirements, the working voltage range is 4.8V~6V.
10) After changes in environmental conditions, the typical time required to achieve stability under reference environmental conditions is at least 12 hours, and at least 19 hours under other environmental conditions.
