This page is related to the Acoustics part of the **Vibrations and acoustics** MECA-H-411 BRUFACE course.

For the Vibrations part, please visit Arnaud Deraemaeker’s page.

**Resources**

- Textbook in French
- Textbook in English
- 2019-2020 Powerpoint set in English: the course being now organized according to the inverted class principles, the slides are no longer presented
*as such*. You may use them as an alternative to the textbook and videos but**I do not**warrant their compatibility with the 2021-2022 course content. - I need help: a discussion page where you can raise questions and (hopefully) get answers !

**Video set and accompanying material**

#### Tuesday September 21st,2021

For the first course, the videos will be shown in the classroom and will be followed by questions, discussions and group exercises.

- 000 – Introduction to the video series – 00’39
- 001 – Definitions – 7’45 – Textbook: section 2.1
- If you wonder when sound has a lasting effect on the propagation media and what kind of effects, watch these two videos on acoustic cavitation and lithotripsy

- 002 – Relevance of acoustics – 4’12 – Textbook: section 2.4
- 003 – Scope of acoustics – 17’48 – Textbook 2.2 and 4.2
- To get a flavor of the scope of acoustic research and review up-to-date topics, you may want to take a look at the title of some of the latest publications in the Journal of the Acoustical Society of America and Journal of the Audio Engineering Society.
- According to your own area of interest, you may look at some of the following videos and additional material.
**Non-linear acoustics:**sonoluminescence, acoustic levitation. **Physiological acoustics:**physiology of hearing (EN, FR), physiology of phonation (EN, FR).**Bioacoustics:**snapping shrimp, singing mice.**Music and musical instruments:**violin, piano, cymbals.**Underwater acoustics:**acoustic thermometry of oceans climate.

- 004 – Hypotheses of linear acoustics – 10’30 – Textbook 4.1

#### Friday September 24th, 2021 – Exercise session 1

- Dynamics of the single degree of freedom system (SDOF) using MATLAB

#### Tuesday September 28th, 2021

- No lecture – Holiday

#### Friday October 1st, 2021 – Exercise session 2

- The ACTRAN acoustic and vibro-acoustic finite element software will be used (1) in some of the future exercise sessions and (2) for the project.
- This session will be dedicated to a presentation of the general working principles of ACTRAN and in assisting the students in installing the ACTRAN software on their own laptops.

#### Tuesday October 5th, 2021

From the second course onward, students are expected to have seen the videos and read the accompanying material **before** the course !

- 005 – One-dimensional propagation – 18’00 – Textbook 4.3 and 4.4 (sections 4.5 and 4.6 are suggested as additional reading material)
- There is no video on
**chapter 5 (Fourier analysis)**because the basics of signal processing, Fourier series and Fourier transforms are assumed to be known. Please read chapter 5 or look at the corresponding slide set if you need a refresher. We’ll do some exercises in the classroom to get everyone up to speed on frequency domain analysis … which will be used throughout the course ! - 006 – Acoustics in the frequency domain – 23’34 – Textbook 6.1 to 6.4 + Section 5.3.2.
- Plane waves and spherical waves in the frequency domain – This topic will be covered in the classroom. Textbook 6.5 and 6.6.
**Note:**Classroom related material will normally only be posted AFTER the classroom. We make an exception here because I’d like to get feedback on videos like this one. It requires a lot of work and if students are not quite interested I will not do more of them. - Here is a note clarifying the definition of (1) instantaneous intensity and its spectrum, (2) active intensity, (3) spectral density of active intensity and its relationship with the cross-correlation of the pressure and velocity signals.
- If you are worried about the notion of phase reference, you may want to look at this note.

- Plane waves and spherical waves in the frequency domain – This topic will be covered in the classroom. Textbook 6.5 and 6.6.
- 007 – The decibel scale – 16’57 – Textbook 7.1 and 7.2.
- Every student is requested to run a Fletcher-Munson-like auditory test and to report the results which will be compiled and presented on October 12th. Here is the Excel report template.

- 008 – More on acoustic levels: weighted levels, band levels, time-dependent levels, statistical levels, white & pink noise – Textbook 7.3 and 7.4

#### Friday October 8th, 2021 – Exercise session 3

- Dynamics of multi-degrees of freedom systems (MDOF) using MATLAB

#### Tuesday October 12th, 2021

- 013 – Acoustic resonance of a closed duct excited by a piston – 07’39 – Textbook 9.1.1.
- For fun: Speaking on Helium

- 014 – More on acoustic resonances – 00’00 – Textbook 9.1, 9.2 and 9.5.
- Resonance frequencies and modes are an essential topic in both acoustics and structural dynamics. Here is a set of four videos proposing a synthesis on the subject. It covers both material already seen in previous lecture and material introducing topics that will be covered in more details later. The four videos are essentially a single long lecture that has been divided in four parts to facilitate their viewing.
- 015a – Three ways to look at SDOF resonances – 13’39 – Not in textbook
- 015b – The 2-DOF system and its two resonances – 04’57 – Not in textbook
- 015c – Dynamic analysis in the modal space – 11’06 – Not in textbook
- 015d – An introduction to continuous systems and their resonances – 12’43 – Textbook 9.1.1.

#### Friday October 15th, 2021 – Exercise session 4

- Dynamics of continuous systems (plates) using ACTRAN

#### Tuesday October 19th, 2021

- 016 – Introduction to vibro-acoustics
- Here is the slide deck that will be presented in the classroom

- Reflection, absorptionandroomacoustics
- 009 – Reflection of acoustic waves hitting a wall under normal incidence – 16’15 – Textbook 8.1
- 010 – Reflection of acoustic waves hitting a wall under oblique incidence – 17’32 – Textbook 8.2. I am not very happy with this video. A new version will be released as soon as possible.
- 011 – Reflection of spherical waves, reflectograms, ray tracing technique – 00’00 – Textbook 8.3
- 012 – Reverberation time and Sabine’s law – 00’00 – Textbook 8.5
- You can play with a simple online RT calculator here.

#### Friday October 22th, 2021 – Exercise session 5

- Resonances of acoustic cavities with ACTRAN
- Sound transmission through a silencer (muffler) with ACTRAN

#### Tuesday October 26th, 2021

- Transmission and insulation

#### Friday October 29th, 2021 – Exercise session 6

- Sound transmission through a plate using ACTRAN

#### Tuesday November 9th, 2021

- Radiation, scattering and refraction

#### Wednesday November 10th, 2021

- Dynamics only – No acoustics content

#### Wednesday November 17th, 2021

- Guided propagation

#### Wednesday November 24th, 2021

- Metrology

#### Wednesday December 1st, 2021

- Practical cases

#### Wednesday December 8th, 2021

- Dynamics only – No acoustics content