Acoustic engineering

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
  • 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 !

Oral exam

The exam dates are January 26 to 28, 2021.

Here is the TENTATIVE question list.

Q&A sessions

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
  • 20.12.2021
  • 21.12.2021
  • 24.01.2022
  • 25.01.2022

Please note that:

  1. 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.
  2. I will leave as soon as the last question is answered … don’t show up at 4:30PM … I will most probably be gone.

ACTRAN Project

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

Note: Nearly all videos have been transferred to YouTube this October 27th. The video numbering has been changed.

Tuesday September 21st,2021

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 0901 – Three ways to look at SDOF resonances – Not in textbook
    • Video 0902 – The 2-DOF system and its two resonances – Not in textbook
    • Video 0903 – Dynamic analysis in the modal space – Not in textbook
  • 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
  • Files:
    • PDF presentation of the two workshops
    • Powerpoint presentation about various aspects of ACTRAN relevant for the workshops
    • Data files

Tuesday October 26th, 2021

  • Debriefing of the exercise session of last Friday
  • Introduction to vibro-acoustics
    • Video 0710 – 1d models
    • Video 0720 – Matrix theory of vibro-acoustics
    • Here is the slide deck that will be presented in the classroom
  • Transmission and insulation

Friday October 29th, 2021 – Exercise session 6

Session 6 content

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
      • There is a direct similitude between acoustic wave reflections and the reflection of bending waves on strings – See the insightful animations created by Dan Russell here. See the actual experiment here.
    • 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 0660 – Spherical waves or acoustic monopoles – Textbook 6.6
      • Video 0830 – Reflection of spherical waves – Ray tracing method – Textbook 8.3
    • Video 0850 – Absorption and reflection coefficients, reverberation time and Sabine’s law – Textbook 8.5
      • You can play with a simple online RT calculator here.
      • Visit the acoustics test rooms (reverberant and anechoic) here.

Wednesday November 10th, 2021

  • Dynamics only – No acoustics content

Wednesday November 17th, 2021

  • Radiation, scattering and refraction
  • Guided propagation:
    • Video 1010 – Propagating vs. evanescent duct modes – Textbook 10.1
    • Video 1021 – TM of simple tube and tube assemblies – Textbook 10.2.1 and 10.2.2
    • Video 1023 – Acoustic resonators and their use – Textbook 10.2.3 to 10.2.5
    • Video 1030 – Transmission Loss and Insertion Loss

Wednesday November 24th, 2021

  • Metrology

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