Absorption co-efficient 1 Absorption coefficient 1 Acoustic wave absorption 1 Architectural acoustics 1 Computational simulation 1 Ensemble average 1 Ensemble averages 1 In situ technique 1 In-situ techniques 1 Measurement techniques 1 Normal impedance 1 Normal impedances Sound absorption characteristic 1 Sound insulating materials 1 Surface normal impedances 1 Velocity control 1