Page 163 - DCAP104_EXPOSURE_TO_COMPUTER_DISCPLINES

Exposure to Computer Disciplines

Notes to justify using the best quality. If the program will be distributed on disk or through the internet,
however, you would consider using lower quality sound to avoid having to distribute many disks
or subject your users to long download times.

7.5.3.2 Sound File Formats
When sound is digitally recorded to a hard disk, a file format is assigned by the recording software.
Sound files are either RAM-based or Disk-based. To play back a RAM-based file, your computer must
have enough random access memory (RAM) to hold the entire file. For example a computer with
8 megabytes of RAM might not be able to play a large RAM-based sound file but a computer with
16 megabytes of RAM might have no problem with it. As a result, RAM-based sound file formats
are appropriate for use with short sound samples. On the Macintosh, System 7 sound and SND
resource are common RAM-based file formats. System 7 sounds are used to generate the various
beeps and alert sounds used on the Macintosh. SND resources are often used as sound resources
in HyperCard stacks. A Macintosh sound recording program, such as MacroMedia’s SoundEdit 16
or the freeware SoundHandle 1.0.3 can be used to create SND resources that can be saved directly
into the resource fork of a HyperCard stack. System 7 and SND file formats are most commonly
used with 22 kHz, 8-bit sound samples.
Disk-based sound file formats allow you to record music of any length and quality. You are
only limited by the amount of available storage space on your hard drive. Disk-based sound
file formats are ideal for longer and/or higher-quality samples. AIFF (Audio Interchange File
Format) is one of the most commonly-used disk-based file formats on Macintosh, Windows,
and even Unix computers. Stereo AIFF sound files recorded at 44 kHz, 16-bit quality are
ideal for multimedia productions that will be distributed on CD. Monophonic AIFF sound
files recorded at 22 kHz, 16-bit quality are better for multimedia productions that will be
distributed via the internet because their file sizes are smaller than higher-quality samples. If
you use the internet frequently you have probably encountered sound files in WAV and AU
formats. The WAV format is used by Microsoft Windows and the AU file format is used by
computers running the UNIX operating system. Sound editing software can convert among
these and many other file formats.
7.5.3.3 MIDI

The Musical Instrument Digital Interface (MIDI) is a hardware and software standard that, among
other things, allows users to record a complete description of a lengthy musical performance
using only a small amount of disk space. Standard MIDI Files can be played back using the sound
synthesis hardware of a Mac or PC. Using a digital audio file format like AIFF, the same symphony
uses over 300 megabytes of hard disk storage. One problem with MIDI is that the quality of the
actual sound you hear will vary depending on the quality of your computer’s sound hardware.
For educational applications, however, MIDI-generated sound can be used to demonstrate musical
ideas quite effectively. Another problem with MIDI in the past was the lack of a standard sound
set. A MIDI file designed to be played with piano and flute sounds might be realized with organ
and clarinet on another person’s computer. This problem was partially solved by the advent of
the General MIDI standard which created a standard set of 128 sounds. Virtually all MIDI files
today are distributed in General MIDI format. Still it was left to the owner of each computer to
be sure their sound hardware could play the General MIDI sounds. Apple Computer solved the
problem with the latest version of its QuickTime software.

156 LOVELY PROFESSIONAL UNIVERSITY