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Example 4: Hemispherical Speaker

General

• A hemispherical speaker is analyzed.
   

• The distribution of sound pressure in the air is solved.
   

• Unless specified in the list below, the default conditions will be applied.
   

• Obtain this session's project file. (Right-click and choose 'Save link as')




• Results will vary depending on Femtet version and the PC environment.

 

Analysis Space

Item	Settings
Analysis Space	3D
Model Unit	mm

 

Analysis Conditions

Item	Settings
Solver	Acoustic Analysis [Mach]
Analysis Type	Harmonic Analysis
Options	N/A

 

The harmonic analysis tab is set up as follows.

The sound waves propagate outside the analysis region. Therefore the [open boundary] condition below is applied initially.

The default conditions are applied.

Tab	Setting Item	Settings
Harmonic analysis	Frequency: Sweep Values	10 [kHz]
	Frequency: Sweep Type	Single Frequency
	Frequency Sweep	Discrete Sweep
Open Boundary Tab	Type	Absorbing Boundary
	Order of Absorbing Boundary	1st-order
	Coordinates of Origin	x = y = z = 0

Model

The air hemisphere is created from a solid body. The open boundary is set on the surface of the hemisphere.

A circular sheet body is defined for imprinting.
The velocity boundary condition is applied.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
0/Solid	Air	000_Air(*)

* Available from the material DB

 

The sound speed of air is set as follows.

Material Name	Tab	Settings
000_Air(*)	Sound Speed	3.4X102 [m/s]

Boundary Conditions

The [speed] boundary condition is set on the face of the imprinting body.

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Settings
Open/Face	Acoustic	Open Boundary
VEL/Face	Acoustic	Speed	1 [m/s]

Results

The gradation contour of the sound pressure at the driving frequency of 100 [Hz] is shown below.