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If Linear elastic is selected, absorption by the medium is neglected, so no other inputs are required.
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If User-defined attenuation is selected, select an option from the Attenuation type list. The default is Attenuation coefficient, Np per unit length.
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For Attenuation coefficient, Np per unit length enter a value or expression for the Attenuation coefficient α (SI unit: Np/m). The default is 0. Note that this is the attenuation coefficient of the pressure amplitude rather than the intensity. The ray intensity (neglecting wavefront curvature terms) actually scales as I(x) = I0exp(−2αx), where x is the propagation distance.
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For Intensity attenuation coefficient, Np per unit length enter a value or expression for the Intensity attenuation coefficient m (SI unit: Np/m). The default is 0. Neglecting curvature terms, the ray intensity decreases as I(x) = I0exp(−mx).
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In most room acoustics references the attenuation coefficient given is the intensity attenuation coefficient m. When setting up models it is important to know which definition is used and choose between the preceding two options accordingly.
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For Attenuation coefficient, dB per unit length, enter a value or expression for the Attenuation coefficient α' (SI unit: dB/m). The default is 0.
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For Attenuation coefficient, dB per wavelength, enter a value or expression for the Attenuation coefficient α(λ) (SI unit: dB). The default is 0.
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Temperature T (SI unit: K, default 293.15 K)
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Relative humidity (dimensionless, default 0)
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Temperature T (SI unit: K, default 293.15 K)
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Depth D (SI unit: m, default 0)
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The Practical salinity is defined on the Practical Salinity Scale. It represents a specific way of measuring salinity through electric conductivity. Practical salinity is a unitless quantity, although it can be thought of as 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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If Thermally conducting and viscous is selected, specify the following material properties. By default, all fluid properties take default values From material. Choose User defined to enter a value or expression for the:
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Thermal conductivity 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.
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