Introduction to sound

1
Introduction

• Introduction to sound
• The Sound Object
• The methods built into the Sound Object
• Events fired by the Sound Object
• Quirks of sounds
• Example Code
• More examples
• Conclusion

2
What is Sound?

• Sound is movement or vibration of molecules in
  the air. When the wave meets the eardrum you
  experience changes of pressure, the auditory
  nerves vibrate and you hear the sound.
• Sound is represented by sine waves which have two
  characteristics, frequency and amplitude.
• Sound waves vary in frequency (or pitch)
• frequency is measured in HERTZ or Hz
• Sound waves vary in amplitude (loudness or
  volume)
• loudness is measured in DECIBELS or dB

3
What is Digitized sound?

• Is sampled sound. Every so often a sample of
  sound is taken and stored as digital information
  - in bits and bytes.
• How often these samples are taken is the sample
  rate described in Kilohertz shown like this
  11.025 KHz
• The amount of information stored about each
  sample is the sample size and is described in
  bits.
• Sample sizes are either 16 bit or 8 bit. The
  larger the sample size the better it describes
  the recorded sound

4
Digitized sound

• Sound waves are not simple
  sine waves but complex waves
• When you record a sound it is changed from an
  analog (continuous) signal to a digital signal
  using an analog to digital converter (ADC)

each dot a sample taken
5
Determining the size of digital recordings
How do we know we will have enough space to save
a recorded sound?

• Mono
• duration in secs x sampling rate x bit
  resolution / 8 x 1
• e.g. 40 seconds of mono recording _at_ 11 KHz _at_ 8bit
  resolution
• 40 x 11000 x 8/8 x 1 444,000 bytes
• Stereo
• duration in secs x sampling rate x bit
  resolution / 8 x 2
• e.g. 10 seconds of stereo recording _at_ 44 KHz _at_
  16bit resolution
• 10 x 44100 x 16/8 x 2 1,764,000 bytes
• to obtain maximum quality, notice the vast
  difference in size

6
The Sound Object

• The Sound object is for loading, monitoring and
  controlling sound
• It can control individual sounds or all sounds in
  the Flash movie
• Sounds are limited to mono or stereo
• Often you will use sounds which have been
  imported into the library
• but you can load larger files dynamically which
  avoids having a large initial SWF download

7
The Sound Object

• There are two types of sounds in Flash event
  sounds and stream sounds.
• An event sound must download completely before it
  begins playing, and it continues playing until
  explicitly stopped.
• Stream sounds begin playing as soon as enough
  data for the first few frames has been
  downloaded stream sounds are synchronized to the
  Timeline for playing on a Web site.

8
Sound Compression

• Select compression options to control the quality
  and size of sounds in exported movies.
• Select compression options for individual sounds
  using the Sound Properties dialog box, or define
  settings for all sounds in the movie in the
  Publish Settings dialog box.

9
Sound Formats

• WAV (Windows only)
• AIFF (Macintosh only)
• MP3 (Windows or Macintosh)

10
Sound Methods

• Sound.loadSound(URL, streaming)
• Loads an MP3 from a URL, streaming or file-based
• Sound.setPan(value)
• Simple left/right balance of the sound
• Sound.setTransform(object)
• Complex left/right mix and balance of the sound
• Sound.setVolume(value)
• Sets the volume level for a sound

11
Sound Methods

• Sound.start(optional value, value)
• Starts playing a sound from the beginning, or
  from an offset point (really handy why?)
• Sound.stop(optional sound name)
• Stops the specified sound (or all sounds)
  currently playing
• Sound.attachSound(Linkage-name)
• Attaches the library sound specified

12
Sound Methods

• Sound.getVolume()
• Returns the current value of the volume
• Sound.getBytesTotal()
• Returns the total size of the sound in bytes
• Sound.getBytesLoaded()
• Gets the number of bytes loaded so far. Why is
  this useful?

13
Event Handlers

• When a sound finishes loading, the Sound.onLoad
  event fires good time to start playing it
• When a sound stops playing, the
  Sound.onSoundComplete event fires, so you know
  that a new sound can be played safely
• Each time a new ID3 data block has loaded, the
  Sound.onID3 event fires.
• Useful for loading MP3 files and giving more
  details to the user (like the genre, full title,
  recording date and so on)

14
Quirks of sounds

• You can load and play multiple sounds
  simultaneously
• But if the combined volume level tries to exceed
  100, youll get clipping noise
• Great for heavy metal guitars, bad for everything
  else
• You can control sound volume to avoid swamping
  the sound output device
• Or ensure that you play a limited number of
  simultaneous sounds

15
Example Code

• // Creates a sound-handling object
• var mySoundSound new Sound()
• // Starts loading a simple MP3
• // Note - file is not on a streaming server
• mySound.loadSound("touch01.mp3", false)

16
Example Code

• // Starts the sound as soon as it has loaded
• mySound.onLoad function(bOkayBoolean)
• if(bOkay true)
• mySound.start()
• // Could do other things here

17
Example Code

• // The sound has finished
• mySound.onSoundComplete function()
• trace(Sound has finished.")
• // Could do other things here
• //

18
More examples

• To control all sounds in a movie, create a Sound
  object
• var all_soundSound new Sound()
• all_sound.setVolume(75)
• Sets the volume level of all the sounds playing
  to 75 of maximum

19
Conclusion

• Flash has relatively simple sound capabilities
• Easy to use but limited to stereo
• Embedded sound or dynamically loaded
• Supports streaming sounds over the network
• Good control of balance and volume
• Simple event interface
• See Flash help for more details