GypsumBroadband absorber

Physikalisch-Technische Bundesanstalt

Source: H. Lenz, Marktübersicht schallabsorbierende Anordnungen, Ruhr Universität Bochum, 1981, Seite 209

Value from the PTB table, not verified

Knauf Perllit ceiling element No. 3320 with mineral fiber filling

Perllit ceiling element with sound-absorbing filling – No. 3320

PTB reference data

Original description

Material properties

Manufacturer: Knauf Hauptverwaltung Iphofen

Thickness: 1.2 in - 2.8 in

Wall distance: 2 in, 20 in

Hole size: 0.2 in, 0.2 in, 0.3 in

Backing: mineral fiber filling, frame-like reinforced back with trickle protection, taped with aluminum foil

Application: ceiling

Reverberation chamber (ASTM C423 / ISO 354)· 2 variants

NRC

0.40

α_p per octave band

f (Hz)	125	250	500	1k	2k	4k
α_p	0.85	0.50	0.50	0.40	0.20	0.10

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Compare		Value
	20 in	NRC0.40
	2 in	NRC0.45

NRC: 0.40 (derived from ISO 354 lab data)

Weight / density: ca. 20 kg / m²

Dimensions: Länge 30 in, width 335 - 16 in

Measured values as a table (2 measurements)

Knauf Perllit ceiling element No. 3320 with mineral fiber filling: sound absorption coefficient αs per ISO 354 by frequency and test build-up
Build-up	NRC	100 Hz	125 Hz	160 Hz	200 Hz	250 Hz	315 Hz	400 Hz	500 Hz	630 Hz	800 Hz	1000 Hz	1250 Hz	1600 Hz	2000 Hz	2500 Hz	3150 Hz	4000 Hz	5000 Hz
30 - 70 mm · ca. 20 kg / m² · 50 mm	0.45	0.19	0.19	0.20	0.55	0.76	0.92	0.86	0.64	0.44	0.35	0.30	0.24	0.19	0.15	0.11	0.09	0.07	0.04
30 - 70 mm · ca. 20 kg / m² · 500 mm	0.40	0.90	0.96	0.63	0.55	0.48	0.40	0.50	0.52	0.51	0.45	0.38	0.37	0.25	0.22	0.19	0.15	0.12	0.10

Measured values as a table (2 measurements)

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Last updated: 08/28/2026