Analysis Domain Setting

Create a hemispheric body for ambient air. It is centered at the sound source and the radius is R

R must be larger than one fifth the wavelength.

This is the requirement for the open boundary.

If the analysis frequency is 3kHz or higher,

the wavelength is 0.113 [m] (= speed of sound / frequency = 340/3000). R has to be larger than 0.023 [m] (= 0.113/5). Suppose we set R to 20 [mm].

The message below would appear since the frequency is lower than 3kHz and R is less than one fifth the wavelength.

Ignore it for now.

** Warning ** Distance between the wave source and the open boundary is too short. Separate them at least 0.2 wavelength (6.800000e-002).

Set the origin of the open boundary at the center of the ambient air body.

The default setting of 2nd-order absorbing boundary is applied.

By using the boolean subtract,

remove the sound source body from the ambient air because the analysis space consists of only ambient air.