# Acoustic Analysis

This section discusses the applicable scope and methods of acoustic analysis, as well as current problems and needs in the area of acoustic analysis.

## Needs and Applicable Scope of Acoustic Analysis

The applicable scope of acoustic analysis includes the following fields of design development and analysis.

Automobile industry Vehicle interior noise analysis Sound radiated from engine Acoustic analysis under water Noise analysis from home appliances Sound insulation wall, concert hall

There has been growing demand for noise control and reduced development time and costs in these design and development sectors, leading to increased needs and requests for numerical simulation to meet such demand.

## Acoustic Analysis Method

### Sound Modeling

There are various methods according to the technique for modeling behavior related to sound and vibrations.

### Analytical Methods

• Statistics
• Geometrical

#### Wave-based methods (wave analysis methods)

• Finite difference method (FDM)
• Finite element method (FEM)
• Boundary element method(BEM) ⇒ Used by WAON!

### Analytical Model Scale

The element size determining the number of elements and nodes is defined by the wavelength of the upper limit frequency in the analysis. Generally, FEM and BEM require element sizes dividing one wavelength into six.

## Current Situation and Problems of Acoustic Analysis

The boundary element method (BEM) discretizes the boundary of the field subject to analysis into a finite number of elements in order to calculate the physical quantity at any point in the field. BEM is therefore effective for analysis of the following subjects:

• Characteristics of sound radiated from vibrating structures
• Frequency characteristics related to radiated sound enclosed by a specific structure

Compared to FEM, BEM has the advantage of easy element discretization, which is required for analysis, because the BEM method models only the boundary of models; whereas there is a need to calculate the relation between a specific point on the discretized model and all elements in BEM because it generates the general matrix.

With conventional BEM, only up to 11,000 elements could be handled in a general PC environment (1 CPU, 2-GB memory), limiting the scope of application to small models and low-frequency ranges.

## Acoustic Analysis Demand in Recent Years

Over the recent years, there have been the following requests from many acoustic-analysis engineers.

• "Want to be able to carry out accurate simulation based on the wave-theoretical approach in order to grasp sound generation and transmission phenomena."
• "Want to simulate large-scale models in high-frequency ranges."
• "Want to apply acoustic analysis to environment noise problems and cover audible ranges."
• "Want to reduce the costs and time required for simulation."
• "Want to increase mesh divisions and integral points to carry out calculations at higher accuracy."

WAON meets all these needs.
For details, see Product Outline, WAON's Strength: FMBEM.

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