Sound Speed Tab

The material's sound speed is set on this tab.

It is in the [Edit Material Property] dialog box. See [How to Set Body Attribute/Material Property].

Harmonic Analysis

Transient Analysis

Setting Item

Notes

Real Part

Sets the sound speed.

The sound speed in the 1-atm air is given by

331.5 + 0.6*t (t in Celsius)

Imaginary Part/Coefficient of Damping

Sets the imaginary part and coefficient of damping of the sound speed.

The imaginary part indicates the attenuation, which sometimes cannot be ignored in the case of ultrasonics.

Kirchhoff's equation is given below. The sound speed increases

as the frequency increases. See here for more details.

ω: angular frequency, ｃ: sound speed, μ: coefficient of viscosity, ρ: density

γ: heat capacity ratio, κ: thermal conductivity, Cｖ: specific heat at constant volume

It is 2.7x10-7f in the air, and 2.8x10-9f in the water,

where f is the frequency.

The coefficient of damping used for the transient analysis is β in the equation (4') in Technical Notes.

See How to Calculate from the attenuation constant [dB/m].

Frequency Dependency

Selectable only for acoustic-harmonic analysis.

Selects either Yes or No.

If Yes is selected, by clicking , [Frequency-Sound Speed] table will appear.

Enter the frequency, and corresponding real part and imaginary part of the sound speed.