Attenuation of Sound in Air
The attenuation of sound in air at 20°C due to viscous, thermal and rotational loss mechanisms is 1.6E-10f2dB/m. However, losses due to vibrational relaxation of oxygen molecules are generally much greater than those due to classical processes, and the attenuation of sound varies significantly with temperature, water-vapour content and frequency.
ISO 9613-1 : 1993 (E) NOISE ABSORPTION BY AIR
- NPL: Kaye and Laby The speed and attenuation of sound.