rol the smoothing of these distributions individually, <code>'Smooth'</code> can also be given as a three element array controlling the smoothing of the initial pressure, the sound speed, and the density, respectively.</p>

<a name="heading3"></a>
<h2>Defining the time array</h2>

<p>Although <code><a href="kspaceFirstOrder2D.html">kspaceFirstOrder2D</a></code> 
can be used to automatically define the simulation length and time-step (by default <code>kgrid.t_array</code>, <code>kgrid.Nt</code>, and <code>kg