IAT 380: Sound Design

IAT 340: Sound Design Overview

Instructor Information

  • Philippe Pasquier

    • Associate Professor at SFU

    • Contact: pasquier@sfu.ca

Course Highlights

Summary of Previous Weeks

  • Fundamentals of Acoustics and Digital Audio Processing

    • Sound: Its production, propagation, and perception

    • Sonic Waves Representation and Properties:

    • Time vs Frequency Domains:

      • Waveform vs Spectrogram

      • Spectral analysis via Fourier Transform

    • Sound Digitalization:

    • ADC (Analog-to-Digital Conversion) and DAC (Digital-to-Analog Conversion):

      • Sampling Rate

      • Bit Depth

    • Aliasing

    • Quantization Noise

    • Audio File Formats

    • Audio In and Out:

    • Microphones

    • Mixing Consoles or Soundboards

    • Loudspeakers

Digitalising Sound

  • Overview of the audio digital recording and playback chain

Sound Concepts

Frequency Spectrum

  • Spectral Analysis via Fourier Transform:

    • Frequency-Domain Spectrum

    • Time-Domain Waveform

Frequency and Musical Pitch

  • Musical Notation: Related to the fundamental frequency of periodic soundwaves perceived as pitch (notes)

Basics of Editing

  • Editing Art: Visualizing the whole while building in parts

  • Linear Editing:

    • Sequential editing techniques:

    • Cut-and-splice editing techniques

      • Analog audio tapes

      • Analog Film

      • Digital Tapes

    • Destructive Editing:

    • Results in a loss of quality with each copy

  • Non-Linear Editing:

    • Edits made in any order using software tools (e.g., ProTools, Ableton, Reaper)

    • Usually non-destructive editing

Dynamic Range

Dynamic Range and SNR (Signal-to-Noise Ratio)

  • Defined as the ratio of the loudest possible undistorted sound to the quietest or to the noise level of a microphone or loudspeaker

  • Human Hearing Dynamic Range: ±120 dB SPL

  • Digital Audio Dynamic Range: Depends on audio bit depth

Audio Editing Operations

  • Various operations on sound files include:

    • Volume/Gain/Amplitude Modulation

    • Cutting (Fade in/out and Zero Crossing)

    • Normalizing

    • Compression/Expander

    • Reversing

  • Effects:

    • Distortion

    • Time Domain Effects:

    • Phaser, Flanger, Chorus, Time Shifter, Delay

    • Frequency Domain Effects:

    • Filters, Equalization, Pitch Shifter

Editing and Mastering

  • Editing and Mixing:

    • Loading sounds, cutting, sequencing, and adjusting levels

    • Applying effects

  • Mastering:

    • Apply noise reduction

    • Adjust stereo width

    • Finalize track levels and equalize tracks

    • Introduction of reverberation

    • Dynamic expansion and compression

    • Peak limit tracks

  • Bouncing:

    • Choosing export format (lossy vs non-lossy)

    • Selecting portions of timeline to export sound files

The Loudness War

  • Reference to the battle for loudness in music which negatively affects dynamic range

  • Originated with a Metallica album

  • Community response: ongoing discussions and efforts against it

Sound Propagation

Understanding Sound Propagation

  • Direct Sound: Reaches the listener first, providing information about sound location (distance, angular position)

  • Indirect Sound: After reflection, including early reflections to identify room size and reverb sound

Key Concepts of Sound Propagation:

  • Reflection: Most sound is reflected, loudness similar to incoming sound

  • Absorption: Power determined by material used

  • Diffusion: The scattering of sound for desired effect

  • Diffraction:

    • Sound waves bending around objects

    • Example: a concert ticket holder hearing sounds around an obstruction

Effects of Frequency on Propagation

  • Perception of instruments depends on their frequency:

    • High-frequency instruments (e.g., piccolo) heard first due to shorter wavelengths

    • Low-frequency instruments (e.g., bass drum) heard later due to longer wavelengths

The Acoustic “Life Cycle”

  • Phases:

    • Direct Sound

    • Indirect Sound (Early Reflections, Reverberant Sound)

    • Precedence Effect: Perception within 20ms prioritizes direct sound

    • Temporal Fusion Effect: Perception within 20ms includes reflections as part of the sound

Reverberation

Key Characteristics of Reverberation

  • Defined as the time it takes for the sound to die away to a level 60 dB below its original level

Reverberation Time and Its Effects

  • Lengthening factors: Highly reflective surfaces

  • Reverberation Case Studies:

    • Notre Dame for music: 3.5s (pros for music, cons for speech)

    • Most desirable: 1.5 to 2.5 seconds (clarity for speech)

    • .3s (dead sound) leads to issues with hearing

  • Live vs Dead Rooms:

    • Live > 1 second

    • Dead < 500ms

    • Preferences in recording environments encourage recording in 'dead' spaces and adding reverb when mixing

Artificial Reverberation

  • Methods to Generate Artificial Reverberation:

    • Plate Reverb

    • Spring Reverb

    • Acoustic Chambers

    • Digital Reverb

Types of Artificial Reverberation

  1. Plate Reverberation:

    • Mechanical-electronic device using thin steel plates to create long reverb and bright delay

  2. Spring Reverberation:

    • Utilizes transducers and pickups to capture vibrations

    • Often found in guitar amplifiers

  3. Acoustic Chamber Reverb:

    • Highly reflective surfaces, using microphones and speakers, produces natural effects

  4. Digital Reverberation:

    • Hardware/software that emulates reverberation by adding delayed copy of original signal

Convolution Reverb

  • Utilizes impulse response recordings to simulate reverberation from acoustic spaces for realistic effects

Upcoming Sessions and Readings

  • Activating listening sessions focused on Musique Concrète

  • Readings include various chapters and texts relevant to digital sound design

  • Upcoming projects and lab sessions focusing on mastering and applying effects

Sound Sampling and Intellectual Property

Legal Aspects of Sampling

  • Sampling laws are gray; generally, unauthorized samples infringe copyright

Plunderphonics

  • Coined by Oswald, relating to compositions that mimic recognizable sounds with a twist

  • Related but distinct from sampling practices predominant in genres like hip-hop

Quotations to Consider

  • "Music is the poetry of the air" - Jean Paul Friedrich Richter

  • "To listen is an effort, and just to hear is no merit; a duck hears also." - Igor Stravinsky