While propagating through the homogeneuos medium the different frequencies will decay at different rate and if noise sensor is located at
and the noise source is located at
then the acoustic energy decay:
N(r) = N(0) \cdot \exp[-\alpha(f)r] |
The decay decrement is growing with frequency:
.
There is no universal model but it can be approximated by a linear-quadratic dependance:
\alpha(f) = \alpha_1 \cdot f + \alpha_2 \cdot f^2, \quad \alpha_1>0,\, \alpha_2>0 |
with and
having much slower dependance on frequency than
and in most practical cases can be assumed constant.
Physics / Mechanics / Continuum mechanics / Acoustic Noise Propagation