Digital Audio From Compact Disc to the Web

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Digital Audio From Compact Disc to the Web

• Marc Max Jacoby
• VanderCook College of Music

• Analog vs. Digital vs. MIDI
• Recording Essentials
• Internet Uses
• Hardware/Software

Presented at the MidWest Band and Orchestra
Clinic December 2000
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Analog vs. Digital

• Analog sound can be represented as a continuous
  range of values. This can be seen in the motion
  of a speaker cone. The graph of air pressure
  variations from a microphone would look similar
  to the air pressure variations of the speaker on
  playback.

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Sampling

• Digital recording is based on sampling discrete
  moments in time by means of an analog to digital
  converter. The problem is in representing an
  analog signal which contains an infinite amount
  of conceivable numbers into a series of discrete
  numeric representations.

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Sampling

• Sampling is the process of taking snapshots of
  the sound over time.

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Sampling

• Like about 44,000 times per second . . .
• In order to reconstruct a signal, the sampling
  frequency must be at least twice the frequency of
  the signal being sampled. (Nyquist Theorem)

Hi-fi Music 44 kHz Low-fi Music 22 kHz Voice
Quality 11 kHz
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Bit Depth

• Bit depth, much like its counterpart in image
  digitization, is the amount of slots available at
  the sampling points to store a value. Low
  resolution (low bit) systems will require more
  quantization.
• Generally speaking the following is suggested
• Voice Quality 8 bit
• CD quality 16 bit

The video game Pong is an example of a 1 bit
color system.
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Fidelity

• Compare Sampling Rates
• 44k / 16 bit
• 22k / 16 bit
• 11k / 16 bit
• Compare bit depth
• 44k / 8 bit
• 22k / 8 bit
• 11k / 8 bit

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And remember this . . .

• Well, to put it simply, the higher sampling rate
  and bit depth will produce the best fidelity! But
  that will demand one important component in the
  process of digital recording.
• Storage, or hard drive space . . . . . . . and
  DELIVERY!
• It will take about 10 MEGABYTES of disk space to
  store 1 MINUTE of a stereo recording at 44KHz and
  16 bit.
• How much space is on your hard drive right now????

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Digital Audio

• Audio Formats
• AIFF - Audio Interchange File Format (Apple
  format)
• WAV - Windows audio format
• AU - UNIX audio format
• RA/RM - Real Audio (Streaming audio)
• MP3 - MPEG codec
• MIDI - Performance protocol

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MIDI

• MIDI does not deal with sound!
• It is a performance protocol (like a player piano
  roll)
• Small file size
• The client browser and computer will handle the
  audio
• Fidelity depends on user system

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Recording Hardware
Cassette Tape You might have a cassette deck
already. Though, a very high quality deck is
needed to overcome the noise and wow and
flutter (warbly sound). Digital Audio Tape
(DAT) This is a common format in many recording
studios but is not a common consumer
format. MiniDisc This relatively new format
has improved fidelity since its release. CD
Recorder This creates a CD you can play almost
anywhere and is suprisingly easy to use. A
complete recording package can be purchased for
1500 - 2000.
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Recording Hardware
CD Recorder Units start at about 600 - 1000.
Most units can use either CD-R or CD-RW discs.
Mixer or Microphone Preamplifier Since the
signal of a microphone is weak, a preamp or
mixer is needed. A mixer has greater flexibility.
A good stereo preamp will cost 400 and mixers
start around 500. Microphones Expect to pay
about 500 for a pair of good condenser
microphones.
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Computer Hardware
Computer PowerPC Macintosh or better is needed
to record using the computers built in audio
input and output. Pentium Wintel Most
Wintel machines come configured with a sound
card. Storage Hard Drive At least a 1 to 2 GB
drive. You can use the internal drive of your
computer but remember, digital audio takes a lot
of storage space! CD Burner CD is still the most
common media for music. Even if the Internet is
your delivery method, CD is a good cheap backup
system.
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Software

• Peak and SoundEdit 16
• Both are decent quality sound editing packages
  that will allow saving in multiple formats
  including AIFF, WAV, QuickTime, AU, RA.
• SoundEdit comes complete with a variety of
  effects. Some are good, some are not so hot. Peak
  has a few very good effects.
• Best for stereo or mono track editing, tweaking
  sound files, and CD mastering.
• bias-inc.com macromedia.com

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Software

• Deck
• A good mid-level multitrack recording package.
  Can add 4 inputs of effects per track and has a
  decent selection of effects. Can import Standard
  MIDI Files
• bias-inc.com
• Pro Tools Free
• Multitrack recording package. Great audio editing
  features and effects. Also records MIDI tracks!
• And best of all, its FREE!
• digidesign.com

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Software

• QuickTime Pro
• Multi-format converter
• Save audio files in AIFF, WAV, AU
• Convert MIDI files to QT movies
• SoundJam
• A great MP3 encoder. This will allow saving in
  the format that has become so popular on the
  Internet.
• Toast
• A very popular bundled CD creation software.
  Can create audio discs, data discs or a
  combination of the two.

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Good Information

• synthzone.com
• apple.com/quicktime
• mp3.com
• delphi.com/pubweb/audio.html
• real.com
• mediabuilder.com/audiotutor.html