Applied Acoustics course (6 CFU) - Progressive list of lessons

This course is taught in English

This course can be chosen by students of  the following Post-Graduate (Advanced) Degrees: Communication Engineering, Electronics Engineering, Computer Engineering, Mechanical Engineering, Civil Engineering, Environment and Land Management Engineering, Physics, Architecture

Attention: in academic year 2022/23 this course will be held IN PRESENCE.

There will be no synchronous streaming of the lessons, for the reasons clearly explained in this article (in Italian).

Please access the ancillary page containing the progressive list of lessons which also serves as a calendar of the lessons. Here you can download the didactical material, including the video recordings of the lessons which will be done in classroom.

No other platform will be employed (ELLY will NOT BE USED).
 

  
 

Teaching Hours:    Monday, 8.30 to 10.30 - Tuesday, 8.30-10.30 - Room 3 - first lesson is on 19 September 2022

Lecturer: prof. Angelo Farina

E-MAIL: [email protected]

Website: http://pcfarina.eng.unipr.it/ or http://www.angelofarina.it/

Phone Number: 0521-905854 (not recommended)

Receiving hours: Tuesday, 10.30 to 12.30, in building #7 or, better, online using MS teams. This is the link to the "receiving hours" team; you can join this team without the need of asking permission to the teacher using this access code: jzdz20j

The access to receiving hours in presence (in building #7) is possible only after appointment arranged by E-mail, and with the same safety requirements explained above for attending the lessons in presence.

COVID Prevention

BASED ON THE NEW PROVISIONS FOR THE PREVENTION OF THE SARS-Cov-2 CONTAGION issued with prot. n. 225 of 08/09/2022, and taking into account that the teacher is a "fragile subject", IT IS MANDATORY TO

Students are requested to download, read and scrupulously respect the provisions of the aforementioned document, in order to minimize the risk of transmission of the virus among themselves and especially towards the teacher.

We strongly recommend the use of the FFP3 masks made by 3M mod Aura 9330+, the only ones that protect both the wearer (if correctly worn) and the other people present in the room. However, the use of correctly worn FFP2 masks is allowed (sealing the gaps on the sides of the nose by bending the metal headband appropriately); for this course it is not possible to use surgical masks or other non-FFP2 or FFP3 approved masks, or FFP2 masks which are not properly worn all the time.

During each interval the classroom will be ventilated by opening doors and windows to the outside, so, going into the winter, dress appropriately. It is also recommended that you get vaccinated again, as soon as updated vaccines are available.

If for any reason a student does not want or cannot adapt to the restrictive preventive measures referred to above, it is advisable that he does not show up in the classroom and makes use of the recordings of the lessons that will gradually be made available on this web page; he will also be able to make use of the two hours of reception per week, during which the possibility of remote connection via MS Teams is maintained, as clearly indicated here above.

In the unfortunate, but very probable, case that the COVID situation worsens again in the autumn, more restrictive measures may be adopted, including the "green pass" or the return to distance learning. Please consult this page to stay updated on the provisions in place.

 

Contents
 

Introduction

The course of Applied Acoustics is an introductory course to a scientific and technological field undergoing a very rapid development, which offers great employment opportunities (even self-employment, this is one of the few fields where a single professional can still get enough money), and which involves disciplines apparently very different: architecture, structural engineering, physiology, psychology, statistics, physics, electronics, vibration mechanics, fluid dynamics, digital signal processing, telecommunications, measurements, hygiene of the workplace, music, musicology, virtual reality.

Obviously in a post-graduate course of 6 CFUs we can only provide a basic introduction to Applied Acoustics. A full acoustician is formed only through other additional advanced courses, such as courses for Competent Technicians in Environmental Acoustics (6 months, 30 CFUs) or Master Courses (1 year, 60 CFUs) available at some Italian universities, or even dedicated post-graduate degrees (2 years, 120 CFUs, for example the MSC program in Music and Acoustic Engineering of Politecnico di Milano).

Because of its multidisciplinary and transversal nature, the Course of Applied Acoustics is attended by students from various degree programs (almost all branches of Engineering, but also students of Architecture and Physics).

For students of all branches of engineering this is a mind-opening course, it is practically the only opportunity to see (or, rather, hear) the results of the techniques learned in previous courses, in which the purely theoretical foundations of modern advanced mathematical methods are taught. When the "numbers" are transformed in sound, abstruse and difficult mathematical procedures quickly become very clear and immediate, and the possibilities offered by sound editing systems on the PC, used extensively both during lectures and during laboratory exercises, make it possible to listen immediately (usually in real time) to the "effects" of filters or other devices (compressors, gates, convolvers, denoising, etc.).

Given the scientific interests of the teacher, the course covers both the noise-related topics common to all branches of engineering , and the more specific themes relative to the acoustics of theatres and cinemas, audio production in music and television / film, musical instruments, high fidelity recording and Stereo (1D), Surround (2D) and three-dimensional (3D, VR, AR) systems.

The topics are always presented with systematic help of test sounds, as this is the most direct way to make the various operations to be perceived.

EXAMPLE:

Many students do not understand the physical meaning of "differentiation" and "integration" operators applied to a function. Math teachers tend to give "graphical" explanations , such as "the derivative is the slope of a curve" or "the integral is the area under a curve." These explanations are not useful for everyone...

In acoustics, the operations of differentiation or integration modify the spectrum of a sound. In particular, differentiation boosts high frequencies (increases the sound level of 6dB/octave). On the contrary, integration boosts low frequencies. Here's an example, which allows to "listen" to differentiation and integration applied to a recording of the human voice:

Original.mp3

Differentiated.mp3

Integrated.mp3

A more extended presentation of this topic is developed in this web page

Program of the Applied Acoustics course  

  • Physical Acoustics: definition of quantities, propagation of mechanical disturbances in an elastic medium, sound pressure, particle velocity, speed of the sound wave. Equation of the acoustic waves.
  • Energetical Acoustics: sound propagation seen as energy transport. Definition of Sound Intensity and Sound Energy Density. Active and Reactive energy, propagating and stationary sound fields. The Reactivity Ratio (or index).
  • Psychoacoustics: physiological and psychological mechanisms of sound perception by humans. The logarithmic scale of decibels (dB), elementary operations on quantities expressed in dB. Frequency weighting curves, methods of Loudness assessment, frequency analysis with constant bandwidth, with constant percentage bandwidth (octaves, etc.), with critical bands (Bark). Masking phenomena in time and in frequency. Use of psychoacoustics for encoding "lossy" and "lossless" audio signals with large reduction of the "bitrate" required (MP3, WMA, AAC, FLAC, OGG, etc.).
  • Sound Propagation: plane waves, spherical waves, standing waves. Reflection and absorption. Specular and diffuse reflection . Definition of sound absorption coeff. and scattering coeff. . Measurement techniques of the absorption coeff. and of the scattering coeff. .
  • Propagation outdoors: ground absorption, effect of temperature and wind gradients, of air absorption, of shielding or obstacles. The Maekawa and Kurze-Anderson formulas for the estimation of shielding attenuation.
  • Propagation indoors: the phenomenon of multiple reflections, stationary reverberant field. Formulas of the reverberant field and of the semi-reverberant field. Transients when a sound source is switched on and off: sound tail, impulse response of a room, Schroeder backward integration. Definition of Reverberation Time T60 and other quantities related to the acoustic transients. Sabine formula for the estimation of the reverberation time. The apparent sound absorption coefficient, and its measurement by tests in reverberation room.
  • Propagation through building structures: insulation of partitions, windows, tapping noise. Measurement techniques and Italian law.
  • Digital Signal Processing applied to audio and acoustics. Sampling sound, artefacts due to limited amplitude resolution and temporal discretization. Basic algorithms for digital filtering (FIR, IIR): a complex theory made easy. The FFT algorithm, fast convolution, partitioned convolution. Effects of nonlinearities and of time variance.
  • Advanced method for impulse response measurement (MLS, ESS, etc.). Sound quality in concert halls and opera houses. ISO3382 acoustical parameters. Temporal and spatial parameters. Use of directive microphones for assessing the spatial properties of the sound field inside a room.
  • Speech intelligibility in classrooms, auditoria and over telecommunication systems. The signal-to-noise ratio, effect of reflections and reverb. The Speech Transmission Index (STI) and its measurement.
  • Electroacoustics: transducers (microphones, loudspeakers). Devices for processing analog and digital acoustic signal: amplifiers, equalizers, reverbs, compressors, etc... Applications in the audio/electronics industry, in the field of telecommunications and broadcasting, in the recording industry and in entertainment industry automotive, in aviation and marine sectors.
  • Techniques for numerical simulation of sound propagation: finite element models, boundary elements, ray tracing, beam tracing. Using simulation programs, with hands-on practice in the laboratory. 
  • Instrumentation and equipment for acoustical measurements: sound level meter, spectrum analyzer, impulse response measurement system. Virtual Instrumentation on PC, software for acoustical measurements, with practical exercises in the laboratory.
  • Numerical processing of the acoustic signal: from general theory to practical applications on PCs. Auralization, virtual acoustics reality. Outline of modern applications in the entertainment industry, and future uses for "live" real time applications. "Plugins" for digital processing of acoustic effects; FIR and IIR filters, fast convolution, calculation of Inverse numerical filters, active cancellation of sound.
  • The 4 modern methods for measuring absorption coefficients: ISO 354 (reverberation room), ISO 10534 (standing wave tube), the Intensimetric Method (Farina/Torelli), the Impulsive Method (EN 1793/5).
  • Measurement of impulse response and other major acoustic parameters employing Aurora, numerical simulation of the sound field inside a room and outdoors by making use of two calculation programs (Ramsete, Disia).

 

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Didactical Approach

During academic year 2022/23 the lessons are currently planned to be in presence in the classroom. We will perform a new set of audio-video recordings of the lessons done in the classroom. These video recordings will be made available in the Progressive list of lessons, together with other supportive didactical material (old audio-video recordings of some years ago, lesson notes, data files, charts, audio files, etc.).

However, these video lessons are NOT a remote learning course. A proper remote learning course is made of short videos specifically tailored to remote learning and of interactive sessions employing a suitable videconferencing platform, such as Zoom (one of the few capable of high quality stereo audio, which is of utmost importance for this course). Here instead we provide just recordings of classroom lessons, which can be downloaded and watched offline.

An important part of the didactical activities are AUDIBLE EXPERIMENTS and usage of advanced electro-acoustic instrumentation, which are conducted in the classroom at every lesson, and which can only be experienced properly in physical presence in the classroom. Also the interaction with the teacher is fundamental, as at every lesson there is a "questions and answers" period. Furthermore, a number of in class-tests will be done.

In-class tests: a didactical tool, more than an evaluation tool. Some hints:

  1. The input data of the numerical problems are usually dependent on the 6 digits of the matricula number, which are "labelled" in sequence (ABCDEF). For example, if the Matricula number is 123456, then A=1, B=2, etc. - a typical input datum could be: L= 100+F*2 dB, which results in L=112 dB if F was 6. In some cases two digits are employed as a single number: L=100+EF dB results in L=156 dB, if E was 5 and F was 6. Please note, it is NOT the same as L=100+E*F dB, which would result in L=130 dB.
  2. The evaluation of the result is very rigid, as it is being performed by means of an Excel spreadsheet. So the results must be entered VERY EXACTLY: the number must be written with the decimal point (not with a comma); then there must be a space, and finally the correct SI unit (with proper smallcase/uppercase lettering). Examples: 93.5 dB(A) - 340.321 m/s - 5.68E-6 W/m2 - note that the number must follow the Excel notation.
  3. The correction is performed typically during the following lesson.
  4. In case of problems about the scores obtained, the student should ask for explanation by E-mail, and NOT during in-class activity.
  5. During the in-class test the students are allowed, and warmly encouraged, to employ personal computing devices (laptop, tablets, smartphones) also connected to the Internet. These can be used for doing calculations, for accessing the online didactical resources (slides, notes, tables, charts, Excel spreadsheets) and also for free search on the Internet (Wikipedia, internet repositories, etc.).
  6. However, these electronic devices should not be abused, employing social networks or other communication networks finalized to getting help in the solution of the problems. Students caught doing such unethical behaviour will be reported to academic authorities, and risk severe consequence, such as the complete cancelling of their entire academic career and the expulsion form the University of Parma. Students are warned of the high risk that these electronics devices can cause, so use them very carefully, because the risk is strongly exceeding the potential advantages that an unethical behaviour can provide.
  7. Students making use of their personal computing devices are warmly encouraged to use them also for submitting "online" the results of the tests, by filling up a Google Form. The link to it will be provided just at the moment of the test, and will be deactivated after a few minutes, at the end of the test. For filling up the questionnaire each student must first login his web browser to Gmail, using his student's credentials ([email protected]). The following link provides a test questionnaire, for checking your connectivity and your capability of compiling a Google Form properly:

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Method of Examination

The method of examination is in two parts:

1) mandatory intermediate written tests, usually in person in the classroom, or exceptionally online. The few students who cannot attend to in-class tests can be required to perform an alternative written test before the oral exam.

2) a simple oral exam, during which the student must answer to theoretical questions and solve some problems (including numerical calculations, so an hand-held calculator is required).

In both parts the student must be equipped with tables, charts, and any other support material required for solving numerical problems.

In case of public health problems related to COVID-19, both the intermediate tests and the final oral exam can be done online.


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Electronic registration of exams

Starting in January 2015, the standard procedure for registering exams during the official exam dates shown above is the electronic one, employing ESSE3 (https://unipr.esse3.cineca.it).

This means that every student must enlist for the exam on Esse3. And for doing that, the student must have got an approved study's plan, and must have completed the evaluation questionnaire for this course.

Students who cannot enlist on Esse3 cannot make the exam: in no case the teacher will perform manual verbalization or wait to register the exam until a following exam session. Please contact the didactical secretary for problems with Esse3, and not the teacher, who has no control on that system.

If, for any reason, the student cannot enlist on Esse3, there is no point contacting the teacher, as he cannot do anything for solving this problem.

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Recommended textbooks

The official textbooks for the Applied Acoustics course are:

These books are in Italian - free download in PDF format, you can also request for a free hardcopy to Rockwool. Thanks Rockwool!

The books RECOMMENDED (not mandatory) for thorough preparation of the exam are:

Additional support material for the course (Excel spreadsheets, WAV files, etc..) used during the lessons will be made available in the "Public" section of this website:
http://pcfarina.eng.unipr.it/Public/Applied-Acoustics/2022/ - It is recommended to download especially the Excel spreadsheets containing the exercises done in the classroom.

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Audio / Video recording of the lessons

Starting from academic year 2010/2011, we are performing audio / video recording of the lessons, in AVI or MKV format, thanks to the Open Source program OBS Studio .

The following link points to a page containing a selection of these audio-video recordings, corresponding to the scheduled numbering of the lessons.

Progressive list of lessons

For each lesson the student can download:

It is recommended to use the Open Source program VLC Mediaplayer for viewing and listening to these AVI or MKV files on any platform (Win/Mac/Linux). We also recommend to first download these video files to a local directory, and then to open the files form the local HD employing VLC mediaplayer. Playing back directly in the browser, from the course web site, is NOT recommended...

Prior of each lesson, the students should download and watch the previous' year audio/video recording, keeping an eye on the Note, so that they will get a background, albeit crude, of the topic which will be developed in class. After the lesson is done, the new recording will be made available, usually within a week.

Software

This is the list of software used during the lessons and lab sessions, with links to download them.

Name

Description

Link

 Adobe Audition

Program for sound recording and playback, waveform editor, simple FFT analysis, sonogram, multitrack recorder, and it can act as a "host" program for plugins in three different formats (VST, Direct-X, XFM).

The recommended versions are 1.5 (the best one) and 3.0 (if you need ASIO). An unrestricted version of Audition 3.0 can actually be downloaded for free from the Adobe web site linked here beside, after registering.

Please DO NOT USE version 2.0 or version CS 5.5 and following (CC), as these are NOT compatible with Aurora plugins. And please, install the English version of Audition (and of any other program offering a multi-language interface!).

Furthermore, it is always mandatory to set the Regional Settings of your operating system (in Control Panel) to English-UK or similar, NEVER in Italian! This affects decimal separator, date, time and number formats... If this setting is incorrect, operations such as Copy and Paste to another program (i.e., Excel) are going to fail....

https://helpx.adobe.com/creative-suite/kb/cs2-product-downloads.html?promoid=19SCDRQK

 Aurora

Suite of XFM plugins for Adobe Audition: generation of test signals (MLS, sweep) computation of the impulse response, acoustic parameters according to ISO 3382, calculation of inverse filters. Includes a fast convolution module, which is employed for performing auralization. 

See the warnings above for Audition regarding program version and regional settings.

Aurora is shareware, with a "russian roulette" annoying-by-purpose feature.

http://www.aurora-plugins.it

 AudioMulch

VST-Host general purpose program, programmable through the construction of block diagrams, coming with a wide range of effects. Easy to use. Versions for Windows and Mac.  90 days free trial.

http://www.audiomulch.com

 Plogue Bidule

VST-Host general purpose program, programmable through the construction of block diagrams, coming with a wide range of effects. It is possible to create new effects. Shareware. Windows and Mac versions. It can also be used as a VST plugin inside another VST Host program. More tricky than Audio Mulch, but also more powerful.  90 days free trial.

http://www.plogue.com/

 SynthEdit

VST-Host program and compiler of VST plugins, programmable through the construction of block diagrams. Customizable interface with editable "skins". Contains an extensive library of graphical objects and of processing functions. Shareware. Better than Labview ....

http://www.synthedit.com/

 SpectraPLUS

FFT and fractional-octave frequency analysis, cross-spectrum, sonogram, waterfall, signal generator for acoustic testing, measurement of reverberation times. Works with one or two channels, can be used to record and analyze WAV files. 30 days free trial.

http://www.spectraplus.com/

 Ramsete

Simulation of sound propagation in enclosed spaces and outdoors. Calculates the impulse response, and from it derives all the acoustical parameters. Includes a 3D CAD design module and a module for mapping results in colour or by isolevel curves. It also allows for the export of impulse responses in WAV format, for performing auralization. Free trial of the "Lite" version, the crack can be found on Emule, enabling full performance.

http://www.ramsete.com

 DISIA

The package includes Citymap and Disiapyr. These are programs for simulation of noise from road and rail traffic, which can operate both on a large scale (Citymap), and for detailed simulations (Disiapyr). They were developed as part of a DISIA project, funded by the Ministry of Environment, and are the reference computational models for the Italian fleet of vehicles. Free for academic usage (password required).

http://pcfarina.eng.unipr.it/Public/DISIA

Note: the above software is commercial software or shareware (excluding the last one, which is free, but the use is restricted to institutional goals of public administrations, and protected by password), although most of them provide a free running mode for a limited period of time, or indefinitely but with reduced functionality. Users who do not like this approach, can use the following open-source software:

  Audacity

Simple "open source" program for sound recording / playback, with many editing effects; it also operates in multitrack. Supports all platforms (Windows, Mac, Linux). A port of Aurora plugins for Audacity is under development (thesis available).

A special version of Audacity containing some of the Aurora modules so far developed can be downloaded HERE.

Please note that these Aurora modules DO NOT WORK on other versions of Audacity...

http://audacity.sourceforge.net/

 

http://pcfarina.eng.unipr.it/Public/Aurora-for-Audacity/

  Sonicbirth

Compiler for VST and AudioUnit plugis for Mac platform, with graphical interface of "block diagram" type. Interface customizable using editable "skins". It contains a wide library of graphic objects and processing functions. Similar to Synthedit, but less powerful and versatile.

http://sonicbirth.sourceforge.net/

 RoomEQ

JAVA application for the measurement of the impulse response of a room with Exponential Sine Sweep and calculation of equalization filters for sound systems. It includes a realtime spectrum analyzer, a realtime Sound Level Meter, and a reverberation time measurement module.

http://www.hometheatershack.com/roomeq/

 Psysound

Matlab suite of modules, with user interface developed for processing of audio signals and acoustic analysis of all kinds

http://psysound.wikidot.com/

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Copyright (C) Angelo Farina - reproduction prohibited without permission.
Last revised: 20/09/2022