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
  • 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
  • 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.
  • 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.
  • 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
      • 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.
    • 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