OVERVIEW

Acoustics is a key aspect in the development of any engineering product. The concepts covered in the course can be applied to ships, cars, buildings etc. The subject spans from theoretical modelling, measurements, the human perception of sound and vibrations, to practical design solutions.

              This course will provide the fundamentals of engineering acoustics, covering applications such as:  how to assess and improve the acoustics of a room and how to design an effective duct silencer or an vibration isolation system for a machinery. This type of knowledge matches specific requirements from the job-market. 

AIMS AND CONTENT

LEARNING OUTCOMES

The overall aim of the course is to provide skills to promote development of quiet and vibration-free products and processes. The course participants are provided knowledge and skills to carry out a relevant analysis of the sound and vibration characteristics of a product and to define design measures to reduce its noise and vibration. The knowledge provided serves as a basis for further studies in the sound and vibration field.

AIMS AND LEARNING OUTCOMES

After completing the course, the student should be able to:

1. Account for and explain key sound and vibration concepts and quantities.
2. Account for environmental consequences of sound and vibration.
3. Account for, evaluate and critically choose relevant mathematical models and methods to describe important sound and vibration quantities.
4. Apply relevant mathematical models and methods to calculate important sound and vibration quantities.
5. Measure sound emission properties of a product.
6. Measure and assess the hand-arm vibration exposure of a handheld tool.

PREREQUISITES

Basic mathematics including complex numbers and differential equations.

Basic mechanics and solid mechanics.

TEACHING METHODS

• Combined on campus (and if needed in parallel via zoom/teams …) lectures and tutorials. Students prepare by looking at a short video-clip (15 min). A total of  ca 30 minutes for each lecture is envisaged. Short preparation feedback quiz in beginning of lecture.
• Laboratory exercises/demonstrations – Attendance strongly suggested
• Intermediate short exams to promote continuous learning. Participants can pass the exam in this way (with limitations on the mark)

SYLLABUS/CONTENT

The impact of noise and vibration on society

• Impact of noise exposure
• Impact of vibration
• Standards and regulations

Key acoustic concepts and descriptors

• Sound pressure, particle velocity, sound intensity and sound power
• Vibration displacement, velocity, and acceleration
• Strength descriptors: Amplitude, root mean square and the level concept
• Frequency and frequency spectrum.
• Plane wave, spherical wave, wavelength, sound speed

Some useful math and how to use it in acoustics

• Linear systems and frequency response function
• Complex quantities and the so-called  iw-method
• Fourier transformation – From time signals to frequency spectra

The acoustic wave equation and some of its solutions

• From basic equations to the linear wave equation for fluid media
• Plane and spherical wave solutions to the linear wave equation
• Concept of specific acoustic impedance
• Sound intensity in plane and spherical waves

Plane acoustic wave reflection and transmission

• Reflection and transmission of plane waves – Normal and oblique incidence
• Standing waves
• Resonant sound fields

Vibrations and structure-borne sound – How acoustic energy is transmitted via vibrations

• Quasi-longitudinal waves in rods
• Bending waves in beams and plates
• Resonant vibration fields

Statistical room acoustics

• Sabine’s statistical room acoustics model
• Room reverberation time – Acoustic absorption and equivalent absorption area
• Direct field and reverberant field

Acoustic radiation models

• Acoustic monopoles and dipoles
• Acoustic radiation from vibrating surfaces
• Radiation efficiency

Vibration isolation – How to reduce structure -borne sound excitation

• Vibration isolation insertion loss
• Vibration isolation: Point mass-Massless spring-Rigid foundation model

Duct silencers – How to reduce noise from volume pulsations caused by flowing media in ducts

• Reactive vs resistive silencer elements
• Silencer efficiency: Transmission loss and insertion loss
• 4-pole models of reactive duct silencer systems

How to design quiet processes – The excitation force characteristics vs perceived noise

• Some rules of thumb for designing products with low perceived noise levels

2 Laboratory exercises

RECOMMENDED READING/BIBLIOGRAPHY

Course book: Sound and Vibration, Wallin et al.

Collection of problems with suggested answers/solutions

TEACHERS AND EXAM BOARD

Exam Board

ULF CARLSSON (President)

ULF ERIK ORRENIUS (President Substitute)

ENRICO RIZZUTO (President Substitute)

CORRADO SCHENONE (President Substitute)

LESSONS

LESSONS START

See the official calendar of the Polytechnic School 

EXAMS

EXAM DESCRIPTION

Written final exam

Written exam with a problem-solving part and a theoretical/conceptual part.

The problem-solving part consists of 3 problem-solving tasks with 10pts each. Two tasks on basic level and the third on more advanced level.

The essay part consists of 2, 5pts each, short essay tasks intended to examine the understanding och important concepts.

Total maximum 40pts on written exam. 

“Continuous” short exams

Three short written exams, during the course to promote continuous learning. Each short exam contains one, 5pts, short essay tasks and one, 10pts, problem-solving task. The essay task is passed with 3pts or more. The problem-solving task is passed with 6pts or more.

- Pass on all three essay tasks gives 2x5pts = 10pts on the written exam essay tasks.
- Pass on two essay tasks gives 5pts on the written exam 1st or 2nd essay tasks.
- Pass on one essay task gives 0pts on the written exam.
- Pass on three problem-solving tasks gives 2x10pts = 20pts on the written exam's 1st and 2nd problem solving tasks.
- Pass on two problem-solving tasks gives 10pts on the written exam's 1st or 2nd problem-solving task.
- Pass on one problem-solving task gives 0pts on the written exam.

Hence, passing the three short exams allows to complete the course, but does not allow to get more than mark 24.

Grading:
- Mark 30 for 38,5pts <= Sum pts <= 40pts
- Mark 29 for 37,5pts <= Sum pts < 38,5pts
- Mark 28 for 36,5pts <= Sum pts < 37,5pts
- Mark 27 for 35,5pts <= Sum pts < 36,5pts
- Mark 26 for 34pts <= Sum pts < 35,5pts
- Mark 25 for 32,5pts <= Sum pts < 34pts
- Mark 24 for 31,5pts <= Sum pts < 32,5pts
- Mark 23 for 30,5pts <= Sum pts < 31,5pts
- Mark 22 for 29pts <= Sum pts < 30,5pts
- Mark 21 for 27,5pts <= Sum pts < 29pts
- Mark 20 for 26pts <= Sum pts < 27,5pts
- Mark 19 for 24,5pts <= Sum pts < 26pts
- Mark 18 for 23pts <= Sum pts < 24,5pts

ASSESSMENT METHODS

The theoretical/conceptual part evaluates the quality of the examinee’s understanding of important concepts in acoustics.

The problem-solving part evaluates the examinee’s understanding and skills to choose appropriate models and apply them to analyse a given acoustics problem.

Exam schedule

FURTHER INFORMATION

None