﻿ Interference of Sound Waves(2D)Examples | Product | Murata Software Co., Ltd.

# Example3Interference of Sound Waves(2D)

### General

• The interference of sound waves from two sources is analyzed.

• The interference pattern is solved.

• “Field Superposition Setting” function is used to analyze the change in the field when the phase of the driving source is changed.

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

### Analysis Space

 Item Setting Analysis Space 2D Model unit m

### Analysis Conditions

 Item Setting 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.

 Tab Setting Item Setting Harmonic analysis Frequency Minimum: 1000[Hz] Maximum: 2000[Hz] Sweep Type Select Linear step by division number. Division number: 1 Sweep Setting Deselect Fast sweep. Enable each port’s individual weight setting for the superposed field display Select Open Boundary Tab Type Absorbing boundary Order of Absorbing Boundary 1st degree Coordinates of Origin x = z = 0

### Model

The model is created in 2D. A semi-circle and two rectangle sheet bodies form the air.
The “pressure” boundary condition is set on the sound generators. The “open boundary” is set on the perimeter of the semi circle.

### Body Attributes and Materials

 Body Number/Type Body Attribute Name Material Name 5/Sheet Air 000_Air(*)

* Available from the Material DB

### Boundary Conditions

The boundary conditions of open boundary and pressure are set.

 Boundary Condition Name/Topology Tab Boundary Condition Type Setting Open/Face Acoustic Open boundary V1/Face Acoustic Pressure -1[Pa] V2/Face Acoustic Pressure -1[Pa]

### Results

Shown below are the gradation contours of the particle speed at 1000[Hz] and 2000[Hz].

Frequency: 1000[Hz]

Frequency: 2000[Hz]

The interference pattern varies with the frequency.

Next, change the coefficient in the Field Superposition Setting and see its effect. Open the “Field Superposition Setting” dialog box.

The boundary condition names for each driving source (V1, V2) and the corresponding coefficients will appear in the (MAG PHASE) formats.

Initially, (MAG=1.0, PHASE=0.0[deg]) will show up. In this Exercise, we change PHSE of V2 to 0,45,90,180[deg]

and see the change in the field.

The figures below are with the fields set to 1000[Hz], Particle velocity, Magnitude, Absolute, and Linear.

The minimum value of the contour diagram is set to 0[mm/s] and the maximum value to 5[mm/s]. For the easy viewing, the contour is set

with “Gradation contour with color division” selected. By changing the PHASE,

the pattern of the contour is changed. The directivity changes according to the pattern change of the contour as shown below.

Calculation conditions of the directivity are as follows.

Observation point: r=1[m], φmin=0.0[deg], φmax=0.0[deg], φstep=0, θmin=0.0[deg], θmax=180[deg], θstep=60

Display: Select Sound pressure level[dB] and select YZ plane for Reflective. (Calculation is based on the assumption that the wall parallel with Z axis is extending a long distance)

Horizontal axis: Select θ

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