Reference surfaceHighly absorbent
Data source
PTB reference data
Physikalisch-Technische Bundesanstalt
Source: Harris:Handbook of Acoustical Measurements and Noise Control, McGraw Hill 1991
Value from the PTB table, not verified
Ballast or other crushed stone, 3.18 cm, 30.5 cm deep
PTB reference data
Original description
Ballast or other crushed stone, 3.18 cm, 30.5 cm deep
Material properties
Thickness: 12 in
Hole size: 1.3 in
Measurement data
Sound absorption
Reverberation chamber (ASTM C423 / ISO 354)
NRC
0.60
derived from ISO 354 lab data
Frequency values
αp nach ISO 11654
| f (Hz) | 125 | 250 | 500 | 1k | 2k | 4k |
|---|---|---|---|---|---|---|
| αp | 0.25 | 0.60 | 0.50 | 0.55 | 0.75 | 0.65 |
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Value from the PTB table, not verified
NRC: 0.60 (derived from ISO 354 lab data)
Measured values as a table (1 measurement)
| Build-up | NRC | 125 Hz | 250 Hz | 500 Hz | 1000 Hz | 2000 Hz | 4000 Hz |
|---|---|---|---|---|---|---|---|
| Measurement 1 | 0.60 | 0.27 | 0.58 | 0.48 | 0.54 | 0.73 | 0.63 |
Measured values as a table (1 measurement)
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