elec-e5620 audio signal processing · 2017-01-13 · 1/13/2017 1 elec-e5620 audio signal processing...

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ELEC-E5620 Audio Signal Processing

A course on processing of audio signals

using a computer and DSP methods

113 January 2017 V. Välimäki & F. Esqueda

• Vesa Välimäki, course lecturer– Professor of audio signal processing at the Dept. of

Signal Processing and Acoustics

– Research interests: audio effects processing, filters, headphone audio, sound synthesis, musical instruments

• Fabián Esqueda, course assistant– Doctoral candidate at the Dept. of Signal Processing and

Acoustics

– Research interests: digital audio effects, virtual analog modelling, antialiasing techniques

– Contact: [email protected]

Teachers

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V. Välimäki & F. Esqueda

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• A second course on DSP or a postgraduate course

• Course material and lectures in English

• Methods and applications of digital audio signal processing concentrating on musical signals and noise but excluding speech

• Methods needed in research and industry

• All lectures during periods III and IV

• Use WebOodi for registration (IMPORTANT!)− Registration will be closed on Monday, Jan. 16 at 23:59!!!

• Use MyCourses to access slides and submissions folder (https://mycourses.aalto.fi/course/view.php?id=13467).

General Description of the Course

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• We have received very positive feedback from students (average score in 2015: 5.0 and in 2016: 4.75)– “Great course overall.”, “It is an excellent course.”…

– “…pleased with the course as it is now and wouldn't change it too much.”

• No severe criticism– Slightly large workload: 4.0 = “Slightly more” (3.0 would be “just right”)

– “The ‘how’ part is missing with respect to Matlab session.”

• Minor adjustments in 2017– One lecture was deleted (basics), so the workload gets reduced by 8%.

– More Matlab examples will be shown during lectures.

– Lectures and demo topics have been updated (as we do every year).

Previous Feedback and Changes

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• Basics of acoustics and digital signal processing, such as:

1) ELEC-5600 Communication Acoustics (5 cr)

2) ELEC-C5230 Digital Signal Processing Basics (5 cr)

or equivalent knowledge

• Contact Vesa or Fabian, if you are unsure!

Prerequisites

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0. General issues (Vesa & Fabian) 13.1.2017

1. History and future of audio DSP (Vesa) 20.1.2017

2. Digital filters in audio (Vesa) 27.1.2017

3. Audio filter design (Vesa) 3.2.2017

4. Analysis of audio signals (Vesa) 10.2.2017

No lecture (Evaluation week for Period III) 17.2.2017

5. Audio effects processing (Fabian) 24.2.2017

6. Synthesis of audio signals (Fabian) 3.3.2017

7. 3-D sound (Prof. Ville Pulkki) 10.3.2017

8. Physics-based sound synthesis (Vesa) 17.3.2017

9. Sampling rate conversion (Vesa) 24.3.2017

10. Audio coding (Vesa) 31.3.2017

Course Schedule in 2017 (Periods III, IV)

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• …describe the history, trends, and development of digital ASP

• …recognize and design digital filters used in ASP

• …list sound analysis and synthesis techniques and their main features

• …explain how different kinds of audio codecs can be used

• …describe what the concept ‘virtual acoustics’ means

• …apply the provided tools with the MATLAB software in your demo

assignment

Goals: After the course you will be able to

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• Participate in the lectures and make notes

• Concentrate on the big picture instead of every

small detail

• Learning takes time! → Plan your use of time

• Study literature (some good articles are

provided on the course web site)

• Be active, ask questions

Learning Methods

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Option #1: Course assignment (DEMO) + learning diaries & homework− Attend all lectures and be active

− Learning diaries and homework replace the exam

Option #2: Course assignment (DEMO) + exam− Not obligatory to attend all lectures

− Three exams within a year. First option: Monday, May 15, 2017

Course assignment (DEMO):− Team of 2 people

− The end result must include audible sound and visualizations

− Demos will be presented as part of lectures (1-3 demos per week)

Course Requirements

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• Short essays (1-2 pages) based on your lecture notes, containing for example– Highlights of the lecture

– What you learned

– New ideas or insights?

– What was difficult

– Study web links

– Try something out with MATLAB, include plots or links to your processed audio files

– Anything extra you wish to share related to the lecture

Learning Diaries (Option #1)

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• Write the learning diaries like essays– Do not copy sentences from the slides or from the web

– Use your own words – Plagiarism is absolutely forbidden!

– Cite references (e.g. articles and web pages)

• Write only in English please

• Example of an excellent learning diary

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Learning Diaries (cont’d)


• Return 10 learning diaries, one per lecture (min 8)– Not required for lecture #0 (this lecture)– If you must be absent, write an extended diary (max 2). Please contact

Fabian before submitting an extended diary.

• Deadline: Next Thursday after the lecture at 15.45 • Upload to MyCourses

(https://mycourses.aalto.fi/course/view.php?id=13467)– Go to ‘Learning Diary and Homework Submissions’ on the left-hand menu,

there will be a return box for each diary. – You can submit as many times as you like up until the deadline.– Submission grades will be available from the same return box.

• Grading: 0-2 points each– Max: 10 X 2 = 20 points– Min: 8 X 1 = 8 points

Requirements for Learning Diaries

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• For diaries, you will get 0, 1, 1.5, or 2 points2 points means that the diary was of acceptable

length, has good content, and a MATLAB example is shown.

1.5 points: sufficient length and good content.

1 point is awarded for work that is acceptable but too short or otherwise below the standard.

0 points: not acceptable or is missing.

Evaluation of Learning Diaries

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• Return 5 homework solutions during the course– All 5 required to pass the course

• Instructions and deadlines will be on MyCourses

• Grading: 0-2 points– 2 points is very good, 1 point is accepted, and 0 points means

that you need to do better

– Max: 5 X 2 = 10 points

• Total max points = 20 (diaries) + 10 (homework) = 30 p.– By taking the exam, max 30 points can also be gained

Homework Tasks (Option #1)

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• Use MyCourses to submit homework and diaries

– A return box for every submission will appear in the ‘Learning Diaries and Homework Submissions’ section.

• Use the required naming convention for all files

– lastname_lecturenumber_diary.pdf

– lastname_homeworknumber_hw.pdf

• For example: H. Hopo takes part in the third

lecture and writes a learning diary →

hopo_03_diary.pdf

File Upload

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• Alternative to the learning diaries and homework

• Study the lecture slides and literature provided in MyCourses– You will still have to make a demo (course assignment)

• First chance: Monday, May 15, 2017– There will be 3 exams per year

Exam (Option #2)

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• Lecture slides, related articles, and MATLAB examples will be distributed through MyCourses.

Study Material

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Return the Questionnaire

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Demo Team Formation


Demo Topics 2017


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• Implement and compare digital versions of the famous Voltage-Controlled Filter (VCF) used in analog Moog synthesizers!

• Date of presentation: 03.02.2017(L3 Filter design)

• Supervisor: Fabian

• Ref: W. Pirkle, “Virtual Analog (VA) Filter Implementation and Comparisons”, App Note 4,

Demo Topic: Virtual Moog Filters

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Available online at: http://www.willpirkle.com/Downloads/AN-4VirtualAnalogFilters.2.0.pdf

• Measure the frequency response of a loudspeaker and use digital filters to tune it and improve the sound!

• Date of presentation: 03.02.2017(L3 Filter design)

• Supervisor: Juho Liski

• Ref: M. Karjalainen, E. Piirilä, A. Järvinen and J. Huopaniemi, “Comparison of Loudspeaker Equalization Methods Based on DSP Techniques”, J. Audio Eng. Soc., vol. 47, pp. 14–31, 1999.

Demo Topic: Loudspeaker Equalization

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• Implement a digital loudness control function and experiment with it.

• Date of presentation: 03.02.2017 (L3 Filter Design)

• Supervisor: Vesa

• Ref. for analog loudness circuit: Newcomb, A.L., Jr.; Young, R.N. “Practical loudness: An active circuit design approach,” J. Audio Eng. Soc., vol. 24, pp. 32–35, 1976.

Demo Topic: Loudness Control

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http://productionadvice.co.uk/loudness-war-secret/

• Implement a pitch detection algorithm and explore its creative uses.

• Date of presentation: 10.02.2017 (L4 Analysis)• Supervisor: Fabian

• Ref: A. de Cheveigne & H. Kawahara, “YIN, a fundamental frequency estimator for speech and music,” J. Acoust. Soc. Am., Apr. 2002.

Demo Topic: Pitch Detection

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• Implement your own version of this funky electric guitar effect!

• Date of presentation: 24.02.2017 (L5 Effects)


• Ref: P. Dutilleux et al., “Filters and Delays” and V. Välimäki et al., “Virtual Analo Effects,” in DAFX: Digital Audio Effects, 2nd Edition, Chichester, UK: Wiley, 2011.

Demo Topic: Auto Wah

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https://www.boss.info/us/products/aw-3/

• Simulate room reverberation using the new modal approach



Demo Topic: Modal Reverb

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http://www.gikacoustics.com/understanding-decay-times/

• Ref: J. S. Abel et al., “A modal architecture for artificial reverberation with application to room acoustics modeling,” presented at AES 37th

Convention, Los Angeles, CA, Oct. 2014.


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• Explore creative methods to change between songs.

• Date of presentation: 24.02.2017(L5 Effects)


• Ref: A. Härmä & S. van de Par, “Spatial track transition effects forheadphone listening”, in Proc. DAFx-07, Bordeaux, France, Sept. 2007.

Demo Topic: Creative Song Transitions

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• Emulate the famous MXR 100 Phaser guitar pedal!



• Ref: R. Kiiski, F. Esqueda and V. Välimäki, “Time-variant gray-box modeling of a phaser pedal”, in Proc. DAFX-16, Brno, Czech Republic, Sept. 2016.

Demo Topic: Virtual Analog Phaser

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http://www.jimdunlop.com/product/m107-phase-100

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• Implement a digital emulation of the sync effect present in classic analog synthesizers

• Date of presentation: 03.03.2017 (L6 Synthesis)


• Ref: J. Kleimola & V. Välimäki, IEEE Signal Processing Letters, Feb. 2012.

Demo Topic: Osc Sync Algorithms

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http://www.soundonsound.com/sos/nov02/articles/synthsecrets1102.asp


• Implement this new method for reducing aliasing in wavetable synthesis and sampling!



• Ref: A. Franck and V. Välimäki, “Higher-Order Integrated Wavetable and Sampling Synthesis” J. Audio Eng. Soc., Sept. 2013.

Demo Topic: Integrated Wavetable Synthesis

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• Extend the sampling synthesis technique for sounds like fire, rain, ocean waves, and wind.


• Supervisor: Vesa• Ref: D. Schwarz et al.,

“Concatenative sound texture synthesis methods and evaluation,” in Proc. Int. Conf. Digital Audio Effects DAFX-16, Brno, Czech Republic, Sept. 2016.

Demo Topic: Sound Texture Synthesis

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https://slm-assets3.secondlife.com/assets/1917373/lightbox/Crackling%20fire.jpg?1283334519

• Explore the creative uses of flutter echo, a phenomenon we usually try to avoid, using a digital filter model.

• Date of presentation: 17.03.2017 (L8 Physics based sound synthesis)


• Ref: T. Halmrast, “Flutter echo: timbre and possible use as sound effect”, in Proc. DAFx-15, Trondheim, Norway, Nov.-Dec. 2015.

Demo Topic: Flutter Echo

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• Implement a digital version of the famous VCF inside the Korg MS-20 synthesizer, known for its characteristic “dirty” analog sound!

• Date of presentation: 17.03.2017 (L8 Physics based sound synthesis)


• Ref: W. Pirkle, “Modeling the Korg35 lowpass and highpass filters” in Proc. 2013 AES Convention, Los Angeles, CA, October 2013.

Demo Topic: Korg MS-20 Filter

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http://www.vintagesynth.com/korg/korg_ms20_mini_alt_lg.jpg

• Program a virtual analog version of the exotic plate reverb! It’s characteristic sound can be heard in numerous psychedelic records of the 1970’s such as in Pink Floyd’s Dark Side of the Moon.

• Date of presentation: 17.03.2017 (L8 Physics based sound synthesis)• Supervisor: Fabian

Demo Topic: Plate Reverb

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• Ref: V. Välimäki, S. Bilbao, J. Smith, J. Abel, J. Pakarinenand D. Berners, “Virtual AnalogEffects” in DAFX: Digital Audio Effects, 2nd Edition, Chichester, UK: Wiley, 2011.

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• How do you stretch an audio signal while preserving its pitch? What happens to transients? Explore new techniques for realistic time-stretching!

• Date of presentation: 31.03.2017 (L9 Sample rate conversion)


• Ref: A. Moinet, T. Dutoit and P. Latour, “Audio time-scaling for slow motion sports videos”, in Proc. DAFx-13, Maynooth, Ireland, Sept. 2013.

Demo Topic: Time-Stretching (Slow-Motion Audio)

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• Automatically equalize the levels of songs in a music playlist.

• Date of presentation: 31.03.2017 (L10 Audio coding)


• Ref: F. Rumsey, “If it’s loud does that mean it’s bad?” J. Audio Eng. Soc., June 2008.

Demo Topic: Loudness Normalization

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• Why does everyone seem to hate MP3? Time to reveal the artifacts introduced by lossy compression. Do it with a filter!

• Date of presentation: 31.03.2017 (L10 Audio coding)


Demo Topic: What’s wrong with MP3?

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• Ref: K. Brandenburg & G. Stoll, “ISO-MPEG-1 audio: a generic standard for coding of high-quality digital audio,” J. Audio Eng. Soc., Oct. 1994.


L3 ASP17-LinMoogs (Fabian) x

L3 ASP17-LdspkEQ (Juho)

L3 ASP17-LoudnessCtrl (Vesa)

L4 ASP17-PitchDetect (Fabian) x

L5 ASP17-AutoWah (Fabian)

L5 ASP17-ModReverb (Vesa) x

L5 ASP17-SongTranstns (Fabian)

L5 ASP17-Phaser (Fabian) x

L6 ASP17-OscSync (Fabian)

L6 ASP17-IntWavetab (Fabian)

L6 ASP17-TextureSynth (Vesa) x

L8 ASP17-FlutterEcho (Vesa) x

L8 ASP17-MS20 (Fabian) x

L8 ASP17-PlateReverb (Fabian) x

L9 ASP17-SlowMotion (Vesa)

L10 ASP17-LoudnessNorm (Vesa)

L10 ASP17-MP3 (Vesa)

Demo Topics and Dates – Spring 2017

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03.02.2017

03.02.2017

03.02.2017

10.02.2017

24.02.2017

24.02.2017

24.02.2017

24.02.2017

03.03.2017

03.03.2017

03.03.2017

17.03.2017

17.03.2017

17.03.2017

24.03.2017

31.03.2017

31.03.2017


x = taken

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Demo Topics – Summary


• 4 weeks before the demo: Contact your supervisor (Fabian/Vesa)• Meet with the supervisor to plan the demo• Start working on your demo

– Study literature to know what to do– Write MATLAB code and select/generate sounds and figures– Prepare a slide show (max 15 min and ~10 slides)

• A few days before your demo: meet your supervisor again to check audio demos and slides

• Test the demo at latest one day before presentation with Fabian• Present your demo as a part of a lecture!• Return the assignment (document of ~10 pages + code) 4 weeks

after the demo at the latest • You will get max 30 points from your finalized course assignment

Schedule for Demos

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• Go directly to the point– No long history…

• Present logically – The problem – Signal processing solution(s) – Visualization

• MATLAB figures, animations, …– Sound examples

• Sound examples must present a clearly audible effect – Must be heard in the noisy and reverberant lecture hall– It must be clear what to listen to (e.g. original vs. processed sound)

• A good demo will be useful for teaching also later!

What is a Good Demo?

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• Confusing– The audience does not understand what’s going on

– Too many details or lacking essential info

• Meaningless sound examples– For example, minor differences in sound are compared

=> Inaudible for the audience in the lecture hall

• Unclear figures– Axis labels missing, invisibly small font, …

• A bad demo will be useless in the future

What is a Bad Demo?

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• Plan your use of time with a concrete schedule– Take into account other courses/possible assignments and their

deadlines, for example

• 5 credits = 26.7 h X 5 = 133.5 h of work– Lectures take 3 h X 11 = 33 h

– Please plan 133.5 h – 33 h = 100.5 h of work on your own time

• DL: Thursday 19.01.2017 at 15.45 – Return by email (exceptionally this time only) to course address:

[email protected]

Homework #1

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0. General issues (Vesa & Fabian) 13.1.2017

1. History and future of audio DSP (Vesa) 20.1.2017

2. Digital filters in audio (Vesa) 27.1.2017

3. Audio filter design (Vesa) 3.2.2017

4. Analysis of audio signals (Vesa) 10.2.2017

No lecture (Evaluation week for Period III) 17.2.2017

5. Audio effects processing (Fabian) 24.2.2017

6. Synthesis of audio signals (Fabian) 3.3.2017

7. 3-D sound (Prof. Ville Pulkki) 10.3.2017

8. Physics-based sound synthesis (Vesa) 17.3.2017

9. Sampling rate conversion (Vesa) 24.3.2017

10. Audio coding (Vesa) 31.3.2017

Course Schedule in 2017 (Periods III, IV)

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