Page 248 - The Master Handbook Of Acoustics

223
ABSORPTION OF SOUND

Table 9-3 Helmholtz low-frequency absorber perforated-face type.

Depth of Hole Panel x Hole Freq. of
airspace dia. dia. % Perf. spacing resonance
3 8″ 1 8″ 1 8″ 0.25% 2.22″ 110 Hz
5
0.50 1.57 157
0.75 1.28 192
1.00 1.11 221
1.25 0.991 248
1.50 0.905 271
2.00 0.783 313
3.00 0.640 384
3 8″ 1 8″ 1 4″ 0.25% 2.22″ 89 Hz
5
0.50 1.57 126
0.75 1.28 154
1.00 1.11 178
1.25 0.991 199
1.50 0.905 217
2.00 0.783 251
3.00 0.640 308
3 8″ 1 4″ 1 4″ 0.25% 4.43″ 89 Hz
5
0.50 3.13 126
0.75 2.56 154
1.00 2.22 178
1.25 1.98 199
1.50 1.81 217
2.00 1.57 251
3.00 1.28 308
5 8″ 1 8″ 1 8″ 0.25% 2.22″ 89 Hz
5
0.50 1.57 126
0.75 1.28 154
1.00 1.11 178
1.25 0.991 199
1.50 0.905 218
2.00 0.783 251
3.00 0.640 308