With the closure of the bubble structure Armstrong Rubber and Plastic foam insulation materials, opening the structure of the material has better noise performance. In accordance with ANSI / ASTM C423-81a and E795 of the trial, Armstrong will be 20mm thick foam rubber insulation materials directly fixed plate reverberation chamber

	center frequency Hz (bandwidth of 1 / 3 scale)
	125	250	500	1000	2000	4000	NRC
sound-absorbing coefficient volatile specimen Sabins degrees%	0.04 2.6 4.0	0.07 5.0 0.8	0.16 11.0 0.6	0.62 13.9 0.6	0.25 17.3 0.4	0.23 16.2 0.2	0.30

By DIN52218

1 "galvanized pipe fixed way	sound level db (A)	attenuation db (A)
without insulation layer of semi-fixed 1 "tube with Armstrong D-34 semi-insulating pipe fixed 5 / 4" pipe with Armstrong D Insulating Pipe -34 semi-fixed 11 / 2 "tube with Armstrong F-34 insulation tube semi-fixed 11 / 2" tube	53 32 25 23	- 21 28 30
without insulation layer with a fixed tube Armstrong D-34 fixed-tube pipe insulation	53 35	- 18