(Created 2011-09-01.)

ACOUSTICS | VTAF05 |

**Aim**

The purpose with the course is to give knowledge about sound propagation in different media.

*Knowledge and understanding*

For a passing grade the student must

- Be able to describe the physical foundations of waves in solid materials and describe wave propagation in infinite media and structural elements such as rods, beam and plates.
- Be able to interpret fundamental concepts such as acoustic effect, intensity and wave impedance.
- Be able to describe different mechanisms for damping and methods for experimental measurement of damping and have knowledge about how to change the damping properties of a structure.
- Be able to understand and use expressions for point impedance for infinite beams and plates.
- Be able to describe the causes for sound reflection and transmission at blocking elements and understand what happens at a periodic occurance of blocking elements.
- Be able to describe sound radiation from structures.
- Be able to describe the theory for the energy method SEA.
- Understand how sound is propagating in ventilation systems and explain how to attend to ventilation related noise problems.

*Skills and abilities*

For a passing grade the student must

- Be able to calculate the eigenfrequencies, eigenmodes and mode density in finite systems with simple geometries and boundary conditions.
- Be able to analyse a given construction with regards to sound reflection and transmission.
- For a given structural element, be able to design a discontinuity in order to achieve a wanted reflection.
- Be able to calculate the sound radiation from a point-, line- and plane source.
- Easily use concept introduced in the course, such as impedance, loss factor, radiation factor.
- Be able to present the solution of a given acoustic problem in a written technical report.

**Contents**

Different wave types and their respective properties. Longitudinal, transversal and bending waves. Wave propagation in beams and plates. Wave propagation, transmission and reflection in and between different meda. Damping mechanisms and the mathematical description. Plates with damping layers. The concept of impedance. Inimpedance in beams and plates. Transmission of structure bourne sound. Periodical structures. Noise in ventilation systems. Statistical Energy Analysis. Sound radiation from structures. Elementary sound radiators. Acoustics in volumes.

The course contains a larger project task where several of these aspects are included..

**Laborations**

The two course alternatives comprises each three laborations á 4 hours depending on program/specialisation:

E,F,Pi,V: Structural analysis and design:

- Introduction to sound propagation

- Impedance measurement

- Sound propagation in solid media

V: Husbyggnad:

- Reverberation time and eigenmodes in room acoustics

- Sound transmission

- Step sound isolation

**Project tasks**

The two course alternatives each contains a project task depending on chosen specialisation:

E,F,Pi,V: Structural analysis and design:

- Modelling of oscillation in beams and plates

V: Husbyggnad:

- Modelling of flanking and direct transmission

**Literature**

Handed out by the department.

Lecture notes and instructions for construction tasks and laborations.