# Creating materials

In Treble, you can create custom materials to add to your **material library**, allowing you to tailor physical properties of different surfaces to your specific needs and enhance your acoustic simulations and designs.

## Create

To create a new material, click the **+ New** button and in the drop-down menu click **Material**.

You will be prompted with the following popup where you can input the desired absorption coefficients of the material you want to create.

- Name and category fields are required.
- You can set default scattering for your material. For the best results when setting a scattering coefficient we recommend consulting following guide.
- Material description is optional.
- You can upload .txt of .csv files instead of manually inputting desired values.

Alternately you can click the "Input text" button on the right and paste your data in the textbox.

The input should be random incidence absorption data for each octave band, ranging from 63 Hz to 8,000 Hz. Each octave band should be paired with its corresponding absorption coefficient, separated by a space. Provide this data in a sequential list, placing each pair on a new line. e.g.

`63 0.4`

125 0.4

250 0.56

500 0.67

1000 0.56

2000 0.23

4000 0.34

8000 0.56

It is not possible to put in absorption coefficients higher than 0.95

After inputting the desired values in the octave band, click **Start material fit**.

- The material fitter will find a vector of reflection coefficients which best represent the input absorption coefficients, taking into account the random incidence angles of the absorption.
- The fitter will also construct a continuous function to represent the reflection coefficients as this is needed for the wave-based solver.
- The continuous function has a strict format and thus cannot always capture the exact behavior of the reflection coefficients. This can cause deviation from the input values. This mostly happens when there is a high variance between the absorption of the octave bands.
- Keep in mind though, that the uncertainty of the measured absorption coefficients of materials is very high (>± 0.1) and the resulting curve is usually well within those uncertainties.

*See example:*

Here, the resulting fit deviates somewhat from the input coefficients and those numbers will be highlighted in red if they deviate too much from the input coefficients. You can then click **Edit** and tweak the input parameter, before fitting the material again. It can sometimes be necessary to input higher/lower parameters than desired for the fit to move more towards the targeted curve. Your preferences for different frequency bands also matter. Some bands may require precise absorption values, while others may tolerate some deviation from the desired level.

Once an optimal fit of the absorption coefficient/reflection has been obtained and a category has been set for the material, click **Create Material** to confirm the fit and save the material in your library.

The wave-based simulations can handle frequencies up to 2840 Hz. They need the reflection coefficient to perform the calculations, so the material should match well below 2840 Hz. The GA solver uses the surface impedance (which comes from the reflection coefficient) and the absorption coefficients to apply the material. The material fitter gives the GA solver the fitted absorption coefficients for the raytracing engine.

### Material fitter

The material fitter is a behind the scenes calculator that fits absorption coefficients to a reflection coefficient curve (read all about it in our technical reference - here). This can be used for making boundary conditions of surfaces for the wave-based solver and to calculate the phase change of early reflections in the geometrical acoustics solver.

## Delete

To delete a material that you have created yourself, open the material details popup, and click the trashcan in the bottom right corner. A confirmation prompt will appear to confirm the deletion of your material.