BRUEL & KJAER 4188 - Page 131

Chapter 5 — Free-field
1
/
2
" Microphone Type 4191
Effect of Ambient Pressure
Falcon™ Range of Microphone Products
Microphone Handbook
Brüel & Kjær
5
−
26
The typical pressure coefficient at 250Hz for Free-field
1
/
2
" Microphone Type 4191
is –0.007dB/kPa, well within the
±
0.03dB/kPa limits required for Type 0 and Type
1 sound level meters by IEC651.
Fig.5.26 Typical variation in frequency response (normalized at
250Hz) from that at 101.3kPa as a function of change in
ambient pressure
Fig.5.27 Typical effect of ambient pressure on actuator response
(a) at 101.3kPa (b) –40kPa change (c) –80kPa change
(d) at 2kPa
940764e
1k 10k Frequency (Hz)
– 1
0
2
Correction (dB)
1
3
500
50k
– 10kPa
change
– 20kPa
change
– 40kPa
change
940756e
1k 10k Frequency (Hz)
– 20
– 10
10
Response (dB)
0
30
500
50k
20
(d)
(b)
(c)
(a)