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, Theoretical results based on: rf = 12OO rayl rs = ®15 ray l/cm rs = 3Ô5 rayl/cm

5 O 10O -200 BOO 10OO -2000 BOOO 10OOO FREQUENCY, Hz

Figure 7.28 Absorption of Thick Materials with Air Backing (Ingard, 1994)

5 O 10O -200 BOO 10OO -2000 BOOO 10OOO FREQUENCY, Hz

Figure 7.28 Absorption of Thick Materials with Air Backing (Ingard, 1994)

The absorption coefficient of a nonlocally reacting porous layer backed by an air cavity and a rigid wall. The overall thickness of the layer-cavity combination is 20 cm (&") and the different layer thicknesses are 5 cm (2",), 10 cm (4",), 15 cm (&") and 20 cm (&"). The total flow resistance in each case is 2poce.

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