Sound

1
Sound
2
The Program Were Using

• Wavepad
• http//www.nch.com.au/wavepad/index.html

3
Possibilities of Sound

• Bandwidth has always been an issue
• New compression techniques and more people
  getting broadband are making sound more popular
  element in webpages

4
Sound Acronymns

• AIFF
• Audio Interchange File Format
• MIDI
• Musical Instrument Digital Interface
• WAV
• Waveform Audio
• MP3 (MPEG-3)
• Motion Picture Experts Group 3

5
Types of Sound

• Voice
• Blah blah blah
• Music
• La la la
• Sound Effects
• BANG

6
Use of Sound on the Web

• Web Accessibilty
• Helpful for the visually or learning impaired
• Sets mood
• Captures Attention
• Explains
• Can make a website seem more personal
• Sound can be passive or active

7
How Sound Works

• Sound must be digitized as with any
  computer-based media
• Continuous tones are divided into samples. E.g.
  one sample per 44/1000 second means a sample of
  loudness and pitch is recorded 44,000/second (44
  kHz). 44kHz is the sampling rate used for music
  CDs.
• Very true to life, but the bytes add up quickly.
  Most people hear at 22 kHz, so a recording at
  44kHz is indistinguishable from the original.
  When sound is compressed its sampling rate is
  reduced.
• Figure 4.3 shows how sounds are disseminated via
  webpages.

8
MIDI Sound

• MIDI sound is a method for representing sounds
  produced by electronic musical instruments.
• MIDI files are much smaller than other formats.
• MIDI represents instrument, note, duration (3
  bytes).
• E.g. 3 second B flat on a flute takes 3 bytes,
  whereas 44kHz sample requires 132K bytes in other
  sound formats.
• Requires MIDI plug-in.
• Have students find MIDI files on the web.
• Short coming music only. Cannot synthesize
  voice this way. Cannot edit MIDI files with sound
  editing tools.

9
Downloading vs Streaming

• Streaming server sets up a separate connection
  with the listener and sound packets are sent over
  the Internet.
• Multicast vs multiple unicasts.

10
Preparing Sound for the Web

• Hardware
• Microphone
• Speakers
• Analog to digital conversion (connects to
  microphone)
• Digital to analog conversion (connects to
  speakers)
• Storage medium (disk space).

11
Preparing Sound for the Web

• Software
• Sound capture/editing software.
• Table 4.2 surveys some popular software packages.
  Other functions compression, mix tracks, apply
  effects, convert file formats.

12
Blog This

• How can sound be best used for the visually
  impaired? Give examples.