Acoustic Diffusion Model
The Acoustic Diffusion Model is added by default and is used to define the material properties and the governing diffusion equations.
Material Properties
For each of the following properties the default takes values From material, or select User defined to enter a different value or expression in the text field.
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Density ρ (SI unit: kg/m3). The default is 1.2 kg/m3.
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Speed of sound c (SI unit: m/s). The default is 343 m/s.
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Volume absorption coefficient ma (SI unit: 1/m). The default is 0 1/m. This parameter determines the amount of absorption due to losses in the air. The effects are usually of interest in very large rooms/volumes or at very high frequencies. The built-in option Classical viscous and thermal absorption defines the frequency absorption coefficient due to viscous and thermal losses. For the Flat (continuous) band option it is evaluated at the studied frequency feval (the default is 1000 Hz) while it is averaged over the studied band for the other Band Input Type.