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.
The correct figure 18.1 is given below. The low and high damping curves were incorrectly labelled.
The exam dates are January 26 to 28, 2021. Here is the question list and a description of exam modalities.
THREE VERY IMPORTANT REMARKS AFTER RUNNING A TEST EXAM:
- Since you have a defined list of questions to which short answers are expected, you are not allowed to use any type of notes while preparing your answers. To be explicit: no hand written notes, no printed material, no annotated slides, nothing.
- The available time does not give me the possibility to give you any hint, ask for details or try to tease you into giving the appropriate answer. I would like to but I just can’t do it in 15 minutes. You will therefore be evaluated based on what you say, no more, no less. While preparing your answers, calibrate them so that you can say everything that is relevant to a question in two minutes. I will ask you to leave me your preparation notes; I will review them after the exam and they may affect (positively) your note.
- The same applies to the project: convey your message in 5 minutes and leave me your supporting documents. It would help if you were summarizing your work in a one page document that I can review again after the oral examination.
- Textbook in French
- Textbook in English
- ACTRAN download link *** !! to be used only if the standard download procedure failed !! **: download ACTRANSE
- 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 !
I will be available for questions about the course and the project on the following dates in the Paduart room (Solbosch, C Building, 4th floor, BATIR department) from 2PM onward on the following dates:
- 16.12.2021 – CANCELLED (no participant)
Please note that:
- I will come only if at least one student has sent me an e-mail stating that he/she will come to raise questions or discuss some topics.
- I will leave as soon as the last question is answered … don’t show up at 4:30PM … I will most probably be gone.
The afternoon sessions foreseen from week 10 onward (starting on November 15th) are « non-presential ». This is time that is available for you to perform the ACTRAN project whose results must be presented at the oral exam in January.
Here are detailed explanations about the project, about the help you can get from the ACTRAN team. The link also contains all the files required to run the project.
What do I expect from your presentation at the exam:
- a perfect understanding of the results produced by ACTRAN making adequate reference to the theory of chapter 17;
- the presentation of relevant variants of the original model and an ability to explain how the change in such and such input parameter modifies the results.
The project can be made in groups. It seems that 4 students is a reasonable group size.
Video set and accompanying material
Tuesday September 21st,2021
- 000 – Introduction to the video series – Video 0210 – Definitions – 7’45 – Textbook: section 2.1
- Video 0220 and Video 0220b– Scope of acoustics – Textbook 2.2, 2.3 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.
- Video 0240 – Relevance of acoustics – Textbook: section 2.4
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.
- ACTRAN Introduction presentation
Tuesday October 5th, 2021
There is no specific acoustic content for this session (see Arnaud Deraemaeker’s e-mail of October 1st).
Friday October 8th, 2021 – Exercise session 3
- Dynamics of multi-degrees of freedom systems (MDOF) using MATLAB
Tuesday October 12th, 2021
- Three reminders/clarification on SDOF and MDOF. This essentially duplicates things covered in the dynamics part of the course:
- Video 0410 – Hypotheses of linear acoustics – Textbook 4.1
- Videos 0430 and 0430b – d’Alembert solution (1D waves) – Textbook 4.3 and 4.4 (sections 4.5 and 4.6 are suggested as additional reading material)
- Video 0440 – Mechanics of propagation – textbook 4.4.
- 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 !
- Acoustics in the frequency domain:
- Video 0610 – Helmholtz equation – Textbook 6.1 and 6.2
- Video 0630 – Acoustic impedance – Textbook 6.3
- Video 0640 – Acoustic intensity – Textbook 6.4
- Video 0643 – One-sided vs. two-sided spectra in relation to the definition of active intensity.
- 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.
Friday October 15th, 2021 – Exercise session 4
- Dynamics of continuous systems (plates) using ACTRAN
Tuesday October 19th, 2021
- Video 0650 – Plane waves in the frequency domain – Textbook 6.5.
- The decibel scale
- Video 0710 – Sound levels – Textbook 7.1
- Video 0720 -Combining sound levels – Textbook 7.2
- Video 0730 – Band levels, white and pink noise – Textbook 7.3
- Video 0741 – Equal loudness contours and weighted levels (dBA, dBB, …) – Textbook 7.4.1 and 7.4.2.
- Video 0743 – Equivalent and cumulative levels – Textbook 7.4.3 and 7.4.4
- Every student is required to run the Fletcher-Munson-like auditory test from UNSW and to report the results which will be compiled and presented on October 12th. Here is the Excel report template.
- Video 0911 – Acoustic resonance of a closed duct excited by a piston – 07’39 – Textbook 9.1.1.
- For fun: Speaking on Helium
- We’ll calculate acoustic modes under different boundary conditions in the classroom – Textbook 9.1, 9.2 and 9.5.
- Video 904 – An introduction to continuous systems and their resonances – 12’43 – Textbook 9.1.1. – This duplicates info from 013 but also makes an explicit link between the dynamic analysis of continuous systems and acoustics.
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
- Debriefing of the exercise session of last Friday
- Introduction to vibro-acoustics
- Transmission and insulation
Friday October 29th, 2021 – Exercise session 6
Session 6 content
- Sound transmission through a plate using ACTRAN
- Plate-cavity coupling (Step 0 of the ACTRAN project – Pay attention !)
Tuesday November 2nd, 2021
- No lecture – Recovery week
Tuesday November 9th, 2021
- Reflection, absorption and room acoustics
- Video 0810 – Reflection of acoustic waves hitting a wall under normal incidence – Textbook 8.1
- Video 0820 – Reflection of acoustic waves hitting a wall under oblique incidence – Textbook 8.2.
- Video 0822 – Reflection and absorption coefficients – Textbook 8.1.3, and 8.2.2.
- Reflection of spherical waves, reflectograms, ray tracing technique:
- Video 0850 – Absorption and reflection coefficients, reverberation time and Sabine’s law – Textbook 8.5
Wednesday November 10th, 2021
- Dynamics only – No acoustics content
Wednesday November 17th, 2021
- Radiation, scattering and refraction
- Guided propagation:
Wednesday November 24th, 2021
Wednesday December 1st, 2021
- Dynamics only – No acoustics content
Wednesday December 8th, 2021
- Dynamics only – No acoustics content
Wednesday December 15th, 2021
- Acoustics – Wrap-up