Hello,

I am using some code that I have previously successfully used with different geometries to simulate acoustic waves. However, I am getting "maximum supported frequency: 0Hz" no matter what spacial step and temporal step I use. Here is the output of the precomputation:

```
Running k-Wave simulation...
start time: 01-Aug-2019 12:18:09
reference sound speed: 2117.5333m/s
WARNING: visualisation plot scale may not be optimal for given source.
dt: 1ns, t_end: 99.999us, time steps: 100000
input grid size: 300 by 256 by 238 grid points (60 by 51.2 by 47.6mm)
maximum supported frequency: 0Hz
expanding computational grid...
computational grid size: 350 by 306 by 288 grid points
WARNING: Highest prime factors in each dimension are 7 17 3
Use dimension sizes with lower prime factors to improve speed
precomputation completed in 6.2307s
saving input files to disk...
completed in 1.7751s
```

As you can see, my dx in all dimensions is 0.2 mm, and my dt is 1ns. This should satisfy c*dt < dx. What am I missing here?

Thanks,

PC