Sound Absorption Coefficient: It is the amount of sound energy absorbed by the acoustic material, when sound wave incident upon it. Generally, sound absorption is given in terms of Noise Reduction Coefficient (NRC); it is scalar representation of energy absorbed by the surface. It is measured in a two ways as per ISO / ASTM Standards. Normal Incidence Sound Absorption Coefficient-

  • It is measured in a Two Microphone Impedance Tube as per ISO 10534-2 / ASTM E 1050.
  • This technique is good for grading of Acoustic material s only.

Random Incidence Sound Absorption Coefficient-

  • It is measured in a Reverberation Room as per ISO 354 / ASTM C423.
  • It requires a large size sample, but gives actual sound absorption coefficient of the material / component.

Sound Absorption