Medium Properties

Use the node to specify the speed of sound and density of the medium. This node is created by default and includes all of the selected domains for the physics interface.

Pressure Acoustics Model

This section is available if the ray intensity or power is computed in the model. Select an option from the list: (the default), , or . This section determines which additional fluid properties can be specified in the section below.

Medium Properties

The default c (Si unit: m/s) uses values . For enter a value or expression. The default is 343 m/s.

If the ray intensity or power is solved for, the following text fields are available, depending on the option selected from the list in the section:

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If is selected, specify the ρ (SI unit: kg/m3). The default density uses values . For enter a value or expression. The default is 1.2 kg/m3.


	The definition of the attenuation coefficient implemented in the Ray Acoustics interface results in an intensity that scales as I(x) = I0exp(−2αx), where x is the distance traveled (this is not including terms based on curvature) and I0 is the initial intensity. The factor 2α is sometimes referred to as the intensity absorption coefficient. In most room acoustics references this value is called the attenuation constant m. When setting up models it is important to know which definition is used and possibly divide the input data with 2, as α = m/2.

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If is selected, specify the ρ (SI unit: kg/m3). The default density uses values . For , enter a value or expression. The default is 1.2 kg/m3. Enter a value or expression for the Attenuation coefficient α (SI unit: 1/m). Do not confuse this coefficient with the attenuation constant m most often defined in room acoustics (also known as the intensity attenuation coefficient). The two are related through 2α = m.

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For enter the following:

T (SI unit: K) in the section. This can be or taken from the . For the default is 293.15 K.

Sp (dimensionless) in the section. This can be or taken from the . For the default is 35.

D (SI unit: m) in the section. This can be or taken from the . For the default is 0.

pH (dimensionless). The default is 8.


	The Practical salinity is defined on the Practical Salinity Scale. It represents a specif way of measuring salinity through electric conductivity. Practical salinity is a unit-less quantity, although it can be thought off a given in units of g/kg. The default value for the Practical salinity Sp is 35. For details see Ref. 22.

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For enter the following:

T (SI unit: K) in the section. This can be or taken from the . For the default is 293.15 K.

pA (SI unit: Pa) in the section. This can be or taken from the . For the default is 1 atm.

(dimensionless) in the section. This can be or taken from the . For the default is 0.

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If is selected, specify the following material properties. By default, all fluid properties take default values . Choose to enter a value or expression for the:

ρ (SI unit: kg/m3). The default is 1.2 kg/m3.

Cp (SI unit: J/(kg·K)). The default value is 1005.4 J/(kg·K).

γ (dimensionless). The default value is 1.4.

k (SI unit: W/(m·K)). The default value is 0.0257 W/(m·K). For ray acoustics, the thermal conductivity is assumed to be isotropic.

μ (SI unit: Pa·s). The default value is 0.0181 mPa·s.

μB (SI unit: Pa·s). The default is 0.

To define the attenuation coefficient or another medium property as a function of ray properties such as the ray frequency or intensity, the ray variable must be enclosed in the noenv() operator. For example, to use the ray frequency rac.f in an expression for the speed of sound, it must be included as part of the expression noenv(rac.f).


	Attenuation Within Domains