Noise meter measurement calibration should pay attention to matters
1) Reference sound pressure level: 94dB .
2) Reference incident direction: axial direction of the microphone.
3) Microphone reference point: centre of 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 dB 0.2 0.3 0.4 0.5 0.6 0.8
Frequency (Hz) 4k 5k 6.3k 8k 10k 12.5
Correction dB 0.2 0.3 0.4 0.5 4.5 6.2
5) Electrical input device: The equivalent electrical impedance can be used to replace the microphone for electrical signal testing, the capacitance of the equivalent electrical impedance is 20pF, and the insulation resistance is greater than 1GΩ. The shielding cylinder equipped with the equivalent electrical impedance will be rotated on the preamplifier when it is in use.
6) Maximum background noise: When the sound level meter is placed in a low-level sound field and when the microphone is replaced by the above mentioned mating device and shorted out, the maximum possible background noise is 23dB (electrical noise level is 23dB).
7) Allowable *higher* sound pressure level at the microphone: 145dB
8) *Maximum peak input voltage of electrical input devices: 10 Vp-p
9) Operating voltage range when the sound level meter meets the technical requirements: 4.8V~6V.
10) Typical time required to stabilise under reference environmental conditions after a change in environmental conditions: at least 12 h, at least 19 h under other environmental conditions.
