﻿ Resonance in CavityExamples | Product | Murata Software Co., Ltd.

# Example5Resonance in Cavity

### General

• The resonance of sound waves excited in a cavity is analyzed.

• The sound waves radiated from the cavity are peaked when the excitation frequency matches the cavity’s resonant frequency.

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

### Analysis Space

 Item Settings Analysis Space Axisymmetric Model unit mm

### Analysis Conditions

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

The tab setting is listed below.

 Tabs Setting Item Settings Frequency Minimum: 1,000[Hz] Maximum: 10,000[Hz] Harmonic analysis Sweep Type Division number: 190 Sweep Setting Select Fast sweep. Open boundary Coordinates of Origin x = 0 z = 0

### Model

It is axisymmetric, so just right half of the section is created with a sheet body and defined as air. The open boundary is set on the perimeter of the quadrant circle representing the surface of the cavity.

The speed is set as the boundary condition on the bottom of the cavity.

### Body Attributes and Materials

 Body Number/Type Body Attribute Name Material Name 8/Sheet AIR 000_Air(*)

* Available from the Material DB

### Boundary Conditions

The “speed” boundary condition is set on the bottom and the “open boundary” condition is set on the perimeter.

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

### Results

The Figure below is the frequency plot of the sound pressure level [dB] at x=0, Z=10.

It is peaked at 8.9[kHz].

It is very close to 8.46[kHz], the result calculated from the Helmholtz resonance equation below.

 C: Sound speed, V: Volume of cavity

The gradation contour of the sound pressure level at 8.6[Hz] is shown below.

The sound pressure is quite high in the cavity.

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