G.R.A.S. Type 40HT - Page 7

G.R.A.S. Sound & Vibration
Single-channel Low-noise Measuring System consisting of: Type 40HT and Type 12HF - Page 7
Fig. 1.5 Free-eld corrections for various angles of incidence on the ½-inch Microphone Type 40AH.
Fig. 1.6 Typical noise oor of Type 40HT for system and microphone. Shown in ⅓-octave bands for
both the linear and A-weighted cases
100 kHz10 kHz1 kHz100 Hz
Decibelsre.levelat250Hz
- 6
- 4
- 2
0
2
4
6
8
10
180 º
Random incidence
150 º
120 º
0 º
30 º
60 º
90 º
0 º
90 º
120 º
- 8
14
12