As Fig 13, but now for a system with halved lattice spacing.

<p>As <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147206#pone.0147206.g013" target="_blank">Fig 13</a>, but now for a system with halved lattice spacing.</p

Free-field sound level as a function of source-receiver distance, for five values of the kinematic viscosity.

<p>Free-field sound level as a function of source-receiver distance, for five values of the kinematic viscosity.</p

LBM results for a system with a sound source in a Poiseuille flow profile.

<p>Figure (a) shows the horizontal velocity component. Figure (b) shows the density field. Figure (c) shows the excess sound level Δ<i>L</i> at receivers near the lower wall (at the same height as the source, i.e. two lattice spacings above the lower wall).</p

Results of an LBM calculation for a source and receivers at <i>y</i> = 250 and a porous medium below <i>y</i> = 200, showing the sound field at time 1600 (a) and the sound level as a function of distance (b).

<p>Results of an LBM calculation for a source and receivers at <i>y</i> = 250 and a porous medium below <i>y</i> = 200, showing the sound field at time 1600 (a) and the sound level as a function of distance (b).</p

LBM results and analytic solutions for porous and non-porous ground, expressed as the excess sound level Δ<i>L</i> as a function of distance.

<p>LBM results and analytic solutions for porous and non-porous ground, expressed as the excess sound level Δ<i>L</i> as a function of distance.</p

As Fig 4, for a point source and receivers at height <i>y</i> = 50.

<p>As <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147206#pone.0147206.g004" target="_blank">Fig 4</a>, for a point source and receivers at height <i>y</i> = 50.</p

LBM results and analytic solutions from Fig 5B, expressed as the excess sound level Δ<i>L</i> (sound level minus free-field level) as a function of distance.

<p>LBM results and analytic solutions from <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0147206#pone.0147206.g005" target="_blank">Fig 5B</a>, expressed as the excess sound level Δ<i>L</i> (sound level minus free-field level) as a function of distance.</p

Stationary vertical velocity field (a) and density field (b) in a 100x100 LBM system with a porous medium between <i>y</i> = 25 and <i>y</i> = 75 and an upward inflow condition at <i>y</i> = 0, used for estimating the flow resistivity.

<p>Stationary vertical velocity field (a) and density field (b) in a 100x100 LBM system with a porous medium between <i>y</i> = 25 and <i>y</i> = 75 and an upward inflow condition at <i>y</i> = 0, used for estimating the flow resistivity.</p

Schematic illustration of a Poiseuille flow profile.

<p>Schematic illustration of a Poiseuille flow profile.</p

Schematic illustration of upward and downward refraction of sound waves.

<p>Red lines represent curved sound rays.</p