OVERVIEW

Acoustics is a key aspect in the development of any engineering product. 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 a vibration isolation system for a machinery. The concepts covered in the course can be applied to ships, aeroplanes, cars, buildings etc and the type of knowledge you will have after the course matches specific requirements from the job-market.

AIMS AND CONTENT

LEARNING OUTCOMES

The overall aim of the course is to provide skills to support 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 support in the development of silent and vibration free products. Also, 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 teams …) lectures and tutorials. Students prepare by looking at a short video-clip (15-20 min). A total of ca 30 minutes for each lecture is envisaged. Short preparation feedback quizzes are given in the beginning of each lecture.
• Laboratory exercises/demonstrations – Attendance is strongly recommended.
• Intermediate short exams to promote continuous learning. Participants can pass the final exam by successfully participating in the short exams (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 iω-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

Reflection and transmission of plane sound wave

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

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

• Quasi-longitudinal waves in rods
• Bending waves in beams and plates
• Torsional waves in shafts
• 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
• Sound transmission between rooms

Acoustic radiation modes

• Acoustic monopoles and dipoles
• Acoustic radiation from vibrating surfaces
• Radiation efficiency
• Influence of reflecting surfaces

Vibration isolation – How to reduce structure-borne sound transmission

• Vibration isolation efficiency measure – Insertion loss
• Vibration isolation: Point mass-Massless spring-Rigid foundation model
• Vibration isolation: Mobility model

Duct silencers – How to reduce noise from duct flow pulsations

• Silencer efficiency: Transmission loss and insertion loss
• Reactive duct silencer systems
• Resistive silencers
• Reactive vs resistive silencer elements

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

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

Two measurement exercises

RECOMMENDED READING/BIBLIOGRAPHY

Course book: Sound and Vibration, Wallin et al

Collection of problems with suggested solutions and answers

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 

Class schedule

The timetable for this course is available here: Portale EasyAcademy

EXAMS

EXAM DESCRIPTION

Written final exam

The written exam has a problem-solving part and a theoretical/conceptual essay part.

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

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

Total maximum 40 pts on the written exam. 

“Continuous” short exams

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

• Pass on all three short written exam’s essay tasks gives 2x5 pts = 10 pts on the final written exam essay tasks.
• Pass on two out of three short written exam’s essay tasks gives 5 pts on the written exam’s 1st or 2nd essay tasks. Hence, only one of the essay tasks of the final exam, needs to be done.
• Pass on one essay task gives 0 pts on the written exam essay tasks. Hence, both essay tasks on the final exam needs to be done.
• Pass on three problem-solving tasks gives 2x10 pts = 20 pts on the written exam's 1st and 2nd problem solving tasks. Hence, only the last problem-solving task of the final exam needs to be done.
• Pass on two problem-solving tasks gives 10 pts on the written exam's 1st or 2nd problem-solving task. Hence, one of the final exams problem-solving tasks can be skipped.
• Pass on one problem-solving task gives 0 pts on the written exam. Hence, all three problem-solving tasks on the final exam needs to be done.

Hence, passing the three short exams allows to complete the course, but limits the outcome to 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