Introduction to Digital Sound Design (Coursera, February 2013)

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Introduction to Digital Sound Design


Taught by Steve Everett (Emory University)

Week 1: The Nature of Sound

in the ear, physical phenomenon is being translated to electrical pulses, which are then interpreted by our brain

attributes of sound perception:

1) pitch -- frequency of how often air is being compressed; we can perceive ~16-20k vibrations per second

2) loudness (amplitude); height of the compression determines amplitude; not how fast they're going (which is pitch) but their intensity

3) timbre (color or quality of sound; multiple vibrations of different amplitudes, interpreted as color of sound); when you hear a singing tone, you're hearing multiple different pitches that the brain interprets as one

4) duration (length); not fixed, but something we perceive; our sense of "slowness" vs "fastness" tends to be relative to our heartbeat

5) articulation or "envelope" of a sound; first few milliseconds of a sound, it's attack, changes with ifferent instruments

6) diffusion, or sound spatialization; our brain is able to interpret where sound is coming from; different channels (e.g. 10.2 surround sound)

overtone series (also called harmonic or partial series): simultaneously sounding off a particular fundamental frequency (the pitch we hear) plus divisions of it in ratios

when a cello string is plucked, the whole instrument vibrates; we're getting many different frequencies that our ear is processing collectively as the cello

spectrum of the voice -- can identify which frequencies are most prominent (stronger partials)

2/1, 3/1, etc. ratios in the overtone series; all are vibrating at once in a cello to create its timbre (even though we don't hear them individually)

can have quick aesthetic responses based on our experience of timbre

synthesizing sound is building up timbre through addition of different frequencies

sheet music as representation of music, but also a set of instructions for the body, a set of kineaesthetic instructions

music and evolution

  • has promoted group cohesion
  • socio-emotional bonding
  • promotes sexual selection

music in emotional and cognitive development

  • 2 mo old -- prefer consonant to dissonant
  • 2 year old -- recognize happy sounds
  • by age 5 can detect pitch
  • by age 6, can detect both key and harmony
  • tonality fully developed by age 9-12

infants are able to detect mother's timbre even in a crowd

white noise quiets an infant; possibly because of white noise heard in womb (blood rushing, etc.)

auditory roughness -- high ratio partials, highly unstable, pitch instability; concept introduced by Helmholtz (1885)

example of roughness: opening guitar of Jimi Hendrix's "Purple Haze"

how do different cultures develop different preferences for auditory roughness?

Sonic Visualiser,

digital sound vs. acoustic sound -- how does digital sound "make us think and hear in a different way"?

Eric Clarke -- ecological approach to the perception of musical meaning

Barry Schrader -- linear timbral transformations

R. Murray Schafer -- soundscape composition

Barry Truax -- acoustic ecology

Joji Yuasa -- systems of compositional thinking

transportable sound'; Toru Takemitsu says Western music is more 'transportable' than Japanese music; we analyze music as relationship between pitches rather than timbre

musique concrete

object sonore (Pierre Schaeffer) -- acousmatic listening; we don't see the original sound source in digital composition

schizophonia -- pull the music away from cultural contexts and original acoustic environment (R. Murray Schaeffer)

Barry Schrader -- timbres are time-variant structures; constant state of flux in shaping of timbres; "linear timbral transformations" or "timbral morphs"

spectral composition -- evolution of timbral morphs

music teleology, organized from intra- to extra-musical meanings

autonomous listening spaces -- sitting in quiet, contemplative spaces made for experiencing that sound (e.g. concert hall); Kant's notion of "disinterested contemplation," allowing sounds to wash over us in heightened aesthetic experience

expression or experience of emotion

how much motion is embedded in our experience of music? (beats, wave, gesture)

tone painting or sound painting; imitating natural phenomenon

imagery and narrative, painting a story with sound

metaphor of a life experience, creating a social identity

musical affect

ecological approach to musical perception; borrowing from James J. Gibson, philosopher

Clarke, Ways of Listening (OUP, 2005)

  • can't just analyze musical content to understand perception; have to embed the listening in an environment
  • affordances in musical perception; each sound affords certin meaning possibilities
  • musical sounds not fundamentally different than sounds in the natural word
  • listening history of perceiver shapes perception
  • structure of musical environment gives information; perception is collecting that information

Joji Yuasa, associated with Takemitsu and Akiyama movements; interested in musique concrete, computer music, multimedia forms

  • entire system of thinking understanding histories of sound practices

assumptions about electroacoustic music

  • most of us tend to listen teleologically
  • inextricably joined with experience of space

ecological approach as a way of understanding all the different factors related to sound perception

timbral perception as culturally determined; digital sound design / electroacoustic music focuses on timbre over pitch for this reason -- gets at a philosophy of sound

linear --> nonlinear relationships to sound perception; meaning doesn't unfold over time but in space

should technologically produced art be interpreted outside traditional frameworks?

soundscape composition and acoustic ecology; asking:

  • how do our attitudes toward listening and sound-making shape our concepts of music, noise and silence?
  • what are the physical and emotional effects of noise?
  • R. Murray Shafer, Barry Truax, Hildegard Westerkamp, Pauline Oliveros, Luc Ferrari

The Tuning of the World; moving the idea of sound design into a concept of health; what are healthy relationships to sound?

acoustic ecology -- integrated field linked to anthropology and environmental sciences; "composing through sound"

soundscape composition emerged out of acoustic ecology; primary elements:

  • keynote sound; "outline the character of the people living there"
  • sound signals, foreground sounds
  • soundmark, like a landmark -- sound unique to an area

listener encouraged to created the networks of meaning in a soundscape composition

composer's knowledge of the environmental and psychological context of the soundscape materials acknowledged in the composition

Week 2: Music Technology 1

transduction -- converting analogue soundwaves into electrical energy through a microphone

dynamic microphone: membrane or diaphragm at top of microphone that moves by air pressure from sound; pushes against coil of copper, that pushes into a magnetic field (a magnet), that converts waves into electrical pulses; speaker does the reverse process

condensor microphone: two plates at top of microphone, one positive and other negative, sound pushes one closer to the other; requires power to charge plates, either from battery or phantom power from cable; more common in studio recording applications

polar pattern: sensitivity of direction of sound coming into microphone; omnidirectional takes sound from 360 direction; cartioid takes sound from the front and sides (180), with different degree variations; figure 8, or double cartioid

shotgun microphone: very narrow cartioid pattern

frequency response; good microphones give a range up to 20k hertz

impedance: resistance in the XLR cable; low impedance is 600 ohms or less; ground cable (third pin) allows you to shield the signal, so you don't pick up other signals along the way (balanced cable)

high impedance, 50k ohms, very protective of outside interference but can only run it short distances, only need 2-pin connector


only a small bit of electrical energy is coming into the mixer from, e.g., a mic; have to run the signal through a preamp, which is possibly the most important part of a mixer

setting the preamp gain is too low, you have to pump up the volume on the output too much; if the preamp gain is too high, you get distortion

parametric equalizer, with circular knobs, and another knob that sets the band widths; graphic equalizer, uses slide faders for eq spectrums

checking feedback in room; send pink noise (all frequencies) into the sound system, to see which frequencies are amplified in a particular room

can use auxiliary sends to connect to another device (e.g. effects), then bring it back into the output through the auxiliary return; used to send sound to monitor on stage

sound reinforcement: 3 different amplifications; stage sound going to the audience, monitor system, and amps directly linked to guitar

final gain: potentiometer / volume control

tonmeister: specialist in recording a particular quality of sound, being done through mixing

audio file formats

  • uncompressed; WAV, AIFF, AU, raw header-less PCM
  • lossless compression; no data is permanently removed, just compacted to created a 50% reduction
  • lossy compression; takes out data that wno't affect sound to a great degree, but reduction in data per second, 80-90% reduction in file size

16- or 24-bit integers or 32-bit floating-point numbers

PCM: pulse code modulation

lossless: FLAC codec, compressor-decompressor; WavPack (extension .WV); Apple Lossles (.m4a); MPEG-4 SLS, MPEG-4 ALS, MPEG-4 DST; Windows Media Audio Lossless

lossy: mp3 (MPEG-1 or MPEG-2 Audio Layer III; Vorbis (ogg); ATRAC; Musepack or MPC; ACC; WMA lossy

Sequential Circuits -- synth makers in 80s; two engineers devised a Universal Synthesizer Interfact in 1981 and by 1983 were able to demonstrate a MIDI connection between two synths

MIDI command: not full audio information, just computer data (note on, note off, velocity (0-127), pitch bend)

continuous controller information; not just one bit but continuous stream of MIDI data for time-variant performance

MIDI protocol: 8-bit serial transmission with one start bit and one stop bit; 31.25Kbs data rate and asynchronous

5-pin MIDI cable


Control Change, send a program change number to change sound

polyphony: sound generator's ability to play more than one note at a time

sound comes from pre-made patch in or added to the synth

multi-timbral synthesizer; can play multiple different instruments/sounds at the same time

General MIDI System: standardized patch numbers to sounds

MIDI is slow, so was latency difficult on MIDI string instruments

body sensors, environment sensors, video and touch sensors

audio effects

wet and dry signals: dry signal is unprocessed

post- and pre-fader: post-fader, how much goes to effects processing

dynamic range processing

  • difference between quietest and loudest part of the signal
  • can compress or expand dynamic range
  • insert effects
  • compression: narrowing the dynamic range after it reaches a threshold value; changes timbre
  • limiter, expander
  • noise gate: low amplitude maped to zero
  • sidechain input: triggers the effect
  • ducking: reduces the level of one audio signal when another is present
  • gating: commonly used for drums


  • LPF, HPF, BPF (band pass filter), Notch (band reject filter), Wah-wah (band pass filter with time variance)


  • EQ
  • peaking filter (BPF, but effects only narrow range of frequencies)
  • shelving filters: amplifies or attenuates frequences above or below
  • graphic EQ / parametric EQ

time-based effects; memory-based, buffer effect

  • delay
  • echo, delay longer than 50ms
  • chorus, multiple articulations with small delay and pitch change
  • flanging: delay of less than 10ms
  • phasing, shift in spectrum using all pass filter
  • reverb; best used as a send effect; has 1) direct sound, 2) early echoes and 3) dense echoes (multiple bounces)
    • artificial reverb
    • convolution (or sampling) reverb, taking sample from actual space

other effects

  • tremolo, "human rate" amplitude modulation
  • distortion
  • time stretching, pitch changing
  • sample granulation
  • spatialization
  • sound morphing