While fluid percolates through porous media in infinitesimal volume \delta V generates the noise of the power \delta N in a wide frequency range:
| (1) | \delta N = A(f) \cdot {\bf u} \cdot \nabla p \cdot \delta V |
where
{\bf u} | flow velocity |
|---|---|
p | fluid pressure |
A(f) | normalised noise spectrum, \displaystyle \int_0^\infty A(f) \, df = 1 |