Concise Summary of Sound in Multimedia

Overview

  • Introduction to Sound

    • Sound consists of vibrations creating waves of pressure.

    • Sound waves have amplitude (loudness) and frequency (pitch).

    • Acoustics is the study of sound in physics.

    • Loudness measured in decibels (dB).

Digital Audio

  • Represents sound as samples (amplitude at specific times).

  • Quality depends on sampling rate (samples per second).

    • Common rates: 44.1 kHz (CD quality), 22.05 kHz, and 11.025 kHz.

  • Sample size is determined by the number of bits used for amplitude.

  • Digital audio is device-independent with rounded values (quantization).

  • Important considerations:

    • Balance between sound quality and storage resources.

    • Setting appropriate recording levels.

Audio Editing

  • Basic operations: trimming, splicing, volume adjustments on multiple tracks.

  • Advanced processes: format conversion, equalization, time stretching.

  • Audio resolution impacts the accuracy of digitization.

  • File sizes calculated based on sampling rate, bit resolution, and duration.

MIDI Audio

  • MIDI files are lightweight and load quickly.

  • Length of MIDI files can change without pitch distortion.

  • Requires music theory knowledge.

  • Device-dependent and not digitized sound.

MIDI vs Digital Audio

  • MIDI is similar to structured graphics; digital audio is like bitmapped images.

  • MIDI files are smaller and can sound better on quality devices.

  • Digital audio provides consistent playback and does not require music knowledge.

Recording and Editing Digital Audio

  • Can include system sounds for various prompts (e.g., warnings).

  • Different formats exist for storing digitized sounds:

    • AIFF/AIFC for Mac, WAV for Windows.

Audio File Formats

  • Format organizes digitized sound data.

  • Common formats: MP3 (compression), MP4 (audio-video together), ACC (iTunes).

  • CD-ROM/XA enables multiple sessions on one disc.

Adding Sound to Multimedia

  • Determine file format compatibility with software.

  • Decide on type of sound: background music, effects, dialogue.

  • Test sounds for timing accuracy, and maintain high-quality original sound files.

  • Ensure compliance with copyright when using existing sounds.