Chapter 2 — Prepolarized Free-field
1
/
2
" Microphone Type 4188
Dynamic Range
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Microphone Handbook
Brüel & Kjær
2
−
16
2.5 Dynamic Range
Definition
The dynamic range is the range between the upper limit (determined by distortion)
and the inherent noise floor. Both limits are influenced by the preamplifier. This
section gives values for the microphone with and without a preamplifier.
Inherent Noise
The microphone’s inherent noise is due to thermal movements of the diaphragm.
These vary proportionally with the square root of the absolute temperature (in °K).
The inherent noise increases with increasing temperature. With reference to 20°C,
the inherent noise changes by + 0.5dB at 55°C and by − 0.5dB at − 12°C. The
maximum variation of this noise for different samples of Prepolarized Free-field
1
/
2
"
Microphone Type 4188 is
±
1dB.
The preamplifier’s effect on the inherent noise of the combined microphone and
preamplifier depends on the sensitivity and capacitance of the microphone (for
1
/
2
"
Microphone Preamplifier Type 2669, see Fig.2.18 and Chapter 8).
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