CSE5910 : Multimedia Programming in Java

Lecture : Digital Audio

In the previous lecture:

In this lecture:

References: There are many good books on electronic sound and music. This area is so vast that it is ridiculous to pretend that a single lecture can do any more than scratch the surface. I suggest you head to the library and start reading anything on the subject which takes your interest!

Roads, C. "The Computer Music Tutorial", MIT Press 1996

...is however an excellent general text on the subject of computers and music!

guitar player

This material relies heavily on examples played during the lecture. Of course you were there so you knew that!

The Attributes of Sound



frequency spectrum of pitch C4
sin wave tone
(note the fundamental)

frequency spectrum of pitch C4
square wave tone
(fundamental + overtones)


Loudness (Dynamics)

Attack - Decay

Simple model:

More completely specified envelope (ADSR):

ADSR envelope

Different sounds have different envelopes:

piano envelope organ envelope

Digital Audio

hello envelope
Fig 1: Spoken 'hello' waveform
(8 bits per sample, 22kHz sampling rate)

hello wave section

Fig 2: Close-up of spoken 'h...'

hello samples

Fig 3: Extreme close-up of 'h...'

Music, Sound or Noise?

Sound, Little Images and Big Images

Sound For Moving Pictures

Literal Sounds: emerge from a sound source to which the sound refers.

Non-literal Sounds: are not intended to convey a literal meaning, nor be identified with a source.

Source disconnected non-literal sounds do not evoke a visual image of the source.

Descriptive Non-literal Sounds

Sounds can evoke or describe:

  • Moods (like colours)
  • Places
  • Times
  • Attributes (heavy, rough, cold)
  • And more!
  • What do these sound like?

  • Infinity
  • Rough
  • Sharp
  • Soft
  • Hot

    • Icy
    • Heavy
    • Squishy
    • Solemn
    • Potato

    Recording Sounds

    Sounds for Interfaces

    MIDI - Musical Instrument Digital Interface

    A computer can be set up as a software synthesizer to receive and play MIDI messages if it stores at least General MIDI instrument data. MIDI files are MUCH smaller than digital audio files because the sound waveforms are stored or synthesized on the client. Only note information needs to be sent over the Internet, a considerable saving over sending the entire sound waveform!


    Lecture summary:

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