(Created 2009-08-11.)

STRUCTURAL ACOUSTICS | VTA060 |

**Aim**

To give knowledge about wave propagation in different materials and components and use this in order to limit effects of noise.

*Knowledge and understanding*

For a passing grade the student must

- Be able to describe the physical foundation of waves in solid materials and describe propagation of waves in infinite elastic media as well as rods, beams and plates.
- Be able to interpret basic concepts such as acoustic effect, intensity and wave impedance.
- Be able to describe different mechanisms for damping and methods for experimental characterisation of damping and have knowledge of how to change the damping properties of a structure.
- Understand and use expressions for point impedance for infinite beams and plates.
- Be able to describe the cause to reflection and transmission of sound at blocking elements, and understand what happens at periodical repetition of blocking elements.
- Be able to describe the foundation of sound excitation from structures.
- Be able to describe the theory of energy method SEA.
- Have knowledge about numerical calculation methods such FEM and BEM.

*Skills and abilities*

For a passing grade the student must

- Be able to calculate eigenfrequencies, eigenmodes and mode density in finite systems with simple geometries and boundary conditions.
- Given an acoustic construction, be able to analyse it with respect to sound reflection and -transmission.
- Given a structure element, be able to design a discontinuity such that required reflection is achieved.
- Be able to calculate sound excitation from point-, line- and planar sources.
- Be able to use mathematical tools, such as the spacial Fouriertransform and two port matrices.
- Be able to write a small finite element program in CALFEM and use it to analyse a structure element in interaction with a fluid.
- Be able to present the solution of an acoustic problem in a technical report.

**Contents**

Foundations in acoustics are presented. Measures like acoustic power, intensity, wave impedance and sound level are defined. Wave propagation in an infinite, elastic media and rods, beams and plates is discussed. The general field equations for an elastic soil are presented. The principle of Hamilton is frequently used to derive governing equations or to find approximate solutions to acoustic problems. Power methods such as SEA and first order SEA are also included in the course. These aspects are treated together in a larger project

**Literature**

A short course in structure-borne sound, M. Heckl