Instruction Manual

Sound Level Meter Types 2245 – Instruction Manual Page 55 of 110
4.8 Self-generated Noise
Self-generated noise is given for nominal microphone Open Circuit Sensitivity, with
Measurement settings > Input > Sound Field set to Free-field and no microphone
accessories selected.
4.8.1 Maximum Broadband Self-generated Noise
Table 4.1 Maximum broadband self-generated noise
4.8.2 Typical Broadband Self-generated Noise
Table 4.2 Typical broadband self- generated noise
4.8.3 Typical Self-generated Noise Spectra
Typical spectra for self-generated noise are shown in Fig. 4.13 to Fig. 4.14.
Fig. 4.13 Typical self-generated noise, 1/1-octave band
A-weighting
(dB)
B-weighting
(dB)
C-weighting
(dB)
Z-weighting
(dB)
Microphone 16.0 14.8 14.8 16.8
Electrical 11.5 11.2 13.7 20.4
Total 17.3 16.4 17.3 21.9
Frequency Weighting
Maximum
Noise
A-weighting
(dB)
B-weighting
(dB)
C-weighting
(dB)
Z-weighting
(dB)
Microphone 14.9 13.7 13.8 15.5
Electrical 9.8 9.5 12.2 18.8
Total 16.1 15.1 16.1 20.5
Typical
Noise
Frequency Weighting