Sound in multimedia How many of you like the use of

audio in The Universal Machine? What about The Universal Computer? Why or why not? Does your

preference reflect a particular learning style?

Will any of you be using audio in your projects? How?

Measuring sound Sound is measured in decibels (db),

the pressure or volume: typical voice conversation is ~70db, a soft whisper is 30db, a jackhammer is 120db

Decibels measure the energy required to make sounds logarithmically A jackhammer’s noise is about 1 watt, but

voice conversation is 1/100,000 watt

MIDI A notation similar to a musical score A communications standard describing how

electronic instruments and synthesizers play musical sound

Advantages: Often smaller than digital wave form files Can be stretched or edited more easily Exploits quality of good playback instruments

Disadvantages: Playback not reliable, depends on instruments Can’t play speech

Digital audio Windows uses WAV format, Apple uses

AIFF Advantages:

Reliable playback (“what you hear is what you get”) Required for speech playback

Sound effects in \windows\media or the web

Are any of you planning to use simple digitized sound effects in your projects? How so? Where are you getting your sound

effects?

Digitized sound is sampled

        Sampling frequency/rate: how often the sound sample is taken        Sampling size: how much information is stored per sample

Quantization More sampling and more data improves

quality and resolution Value of each sample is rounded off to

nearest integer (hence, quantization) 8-bit sampling size provides 256 bits to

describe dynamic range of amplitude 16-bit sampling size provides over 65

thousand bits for dynamic range, but significantly increases space requirements

Clipping Occurs if amplitude exceeds intervals

Clipping produces hiss or other distortions

Computing the size of a digital recording

Sampling rate * duration (seconds) * (bit resolution / 8) * 1 (mono) or 2 (stereo)

E.g., for a 10 second recording at 20.05 kHz, 8-bit resolution, monophonic (good for speech):

22050 kilohertz * 10 seconds * 8/8 * 1 = 220,500 bytes Or, for 10 seconds of good music quality at 44.1

kHz, 16-bit resolution, stereo: 44100 kHz * 10 * 16/8 * 2 = 1,764,000 bytes

“Red Book” standard (ISO 10149) for CD-quality audio

Expensive for multimedia Playing 16-bit resolution requires 16-bit sound

cards

Compression of digital audio Compression algorithms can reduce file size

by about an order of magnitude Downside? More clipping, sound degradation Authorware: Shockwave Audio (SWA)

Xtras->Other->Convert WAV to SWA Also Voxware (better for speech)

Flash: on import, converts wav to 128kb mp3 Stored automatically as symbols in library Select imported sound from frame properties

Why might it be better to convert some wav files to mp3 outside of Flash?

Compression of digital audio Compression algorithms can reduce file size

by about an order of magnitude Downside? More clipping, sound degradation Authorware: Shockwave Audio (SWA)

Xtras->Other->Convert WAV to SWA Also Voxware (better for speech)

Flash: on import, converts wav to 128kb mp3 Why might it be better to convert some wav files

to mp3 outside of Flash?

Importing sound into Flash

Converts tada.wav to mp3 internally

Flash stores sound as symbols

Click on frame, go to Properties inspector, then select Sound from list

Controlling sounds in FlashEffect options: Sync options:

Event: synchronizes the sound to an event, such as a button click Start: same as event, except it won’t start new instance of new soundStop: silences this sound (also see action StopAllSounds)Stream: keeps sound in sync with animation on a web site; sound won’t play longer than the number of frames it occupies

Tips for recording sound Use a decent quality microphone

Should eliminate noise when silent Choose narrators who speak clearly

Coach your narrator for pronunciation, emphasis A sound editor lets you manipulate sound

Trimming: removing white or empty space Splicing: combining parts of several sounds Amplifying: adjusting volume (for consistency) Re-sampling (e.g., from 16-bit down to 8-bit) Conversion and compression (e.g., wav to mp3)