This article explains some important factors about the Finite Volume Method.

First off, please understand that the Finite Volume Method in Pachyderm is highly experimental. The technique has the potential to be more accurate than geometrical methods, but also has a number of drawbacks, including ram memory, and the difficulty in representing materials. A few things you need to be aware of prior to using the Finite Volume Method in Pachyderm.

1. It does not use Absorption Coefficients or Scattering Coefficients. All boundaries reflect as their geometry dictates without any influence from a numerical scattering coefficient, and all boundaries reflect all energy.

2. Where there is not boundary, we have implemented Perfectly Matched Layers. This means that the edge of the model will absorb as much energy as possible. For high frequencies, this should be close to perfect absorption, but there are some low frequencies for which it is difficult or impossible to absorb all energy.

3. The finite volume method is a very open-ended way of simulating sound, and has not been tested for all applications. If you are trying something, scrutinize the results carefully, and understand that under the terms of the General Public License, you are responsible for the suitability of the way you use the software.

4. There are several panes of the interface that implement pre-designed applications for the finite volume method. These we are fairly comfortable with using for their intended use. These are:

- The Eigenvalue interface: This is useful for identifying peaks in the frequency response of a system, which can be useful for identifying, for example, Room Modes. This is not useful for providing absolute levels in a space.

- The Scattering interface: This is useful for finding the correlation scattering coefficient of a designed shaped finish. The Correlation Scattering Coefficient is (in our opinions) the most useful form of the scattering coefficient for geometrical acoustics simulation. It has an idiosyncratic way of being used, however. The way you build your model is the following: place a sample of your designed finish with its center at the origin (0,0,0). You should specify a 'Measurement Radius' that is wide enough that a sphere with that radius would fully encompass your sample. If it has an airspace behind it, and openings that lead to that airspace, you should specify a "Depth of Sample" for the finish that corresponds to the depth off that airspace. Select a frequency range (understanding that the higher the frequency, the more RAM you will need), and click Calculate.

- Visualzation: This tool is good for... visualization... not much more. If you used the 'Eigen Values' interface, it will have a preset shown to visualize a sine-wave at the eigen-frequency you have selected, which can be useful for purposes of examining, for example, a room mode that has been observed in the eigen-values interface.

If you have questions, please contact me. My door is always open.