1. ASTM E 1050-85a. Test method for impedance and absorption of acoustical materials using a tube, two microphones, and a digital frequency analysis system, Philadelphia, USA, August 1985.
2. ISO 354. Acoustics-measurement of sound absorption in a reverberation room, Geneve, Switzerland, 1985.
3. ASTM C 384-385. Standard test method for impedance and absorption of acoustical material by the impedance tube method, May 1985.
4. Acoustical measurements with a sound intensity meter;Allard;Appl Acoust,1985
5. In situ two-microphone technique for the measurement of the acoustic surface impedance of materials;Allard;Noise Con Eng J.,1989