Multimedia sound

1. 01/07/18
Chapter 4
Sound

2. Overview
• Introduction to sound.
• Multimedia system sound.
• Digital audio.
• MIDI audio.
• Audio file formats.

3. Overview
• MIDI ( Musical Instrument Digital
Interface) versus digital audio.
• Adding sound to multimedia project.
• Professional sound.
• Production tips.

4. Sound
• Sound is energy, caused by
molecules vibrating
• Meaningful Speech in any Language
• Too much volume can permanently
damage your ears and hearing
• The perception of loudness depend
on the frequency or pitch
• Harmonics cause the same note
played on a cello to sound different
from one played on a piano.

5. Power of Sound
• Vibrations in the air create waves of
pressure that are perceived as sound.
• Sound waves vary in sound pressure level
(amplitude) and in frequency (Number of
cycles per time unit) or pitch.
• ‘Acoustics’ is the branch of physics that
studies sound.
• Sound pressure levels (loudness or
volume) are measured in decibels (dB).
• Humans hear sound over a very broad
range.

6. Using Sound in Multimedia
• You need to know
– How to make sounds
– How to record and edit sounds on the
computer
– How to incorporate sounds into your
multimedia project

7. Multimedia System Sounds
• System sounds are assigned to various
system events such as startup and
warnings, among others.
• Macintosh provides several system sound
options such as glass, indigo, laugh.
• In Windows, available system sounds
include start.wav, chimes.wav, and
chord.wav.
• Multimedia sound is either digitally
recorded audio or MIDI (Musical
Instrumental Digital Interface) music.

8. Multimedia System Sounds
• Most computers have sounds ready
to use

9. Multimedia System Sounds
• Mac and Windows have built in
sound recorders

10. Multimedia System Sounds
• Windows system sounds are .WAV
files in the WindowsMedia directory
• MS Office includes additional sounds
• You can add your own sounds by
including them in the
WindowsMedia directory and
selecting them from the Sound
Control Panel

11. MIDI Audio
• MIDI is a series of musical
instructions
Click to play

12. MIDI vs. Digital Audio
• MIDI ( Musical Instrument Digital
Interface) is a communications
standard developed in the 1980’s for
electronic instruments and
computers.
• It allows instruments from different
manufacturers to communicate.

13. MIDI vs. Digital Audio
• MIDI data is NOT digitized sound- it is
music stored in numeric format
• Digital audio is a recording, which depend
on your sound system
• MIDI is a score and depends on both the
quality of the instruments and the sound
system
• Quality depends on end user’s device
rather than on the MIDI device and is
device dependent.

14. Making MIDI Audio
• Creating a MIDI score requires:
– Knowledge of music and some talent
– Ability to play a musical instrument
– Sequencer software
– Sound synthesizer
• Built into PC board
• Add-on for MAC
• MIDI can synthesize over 100 instruments

15. Making MIDI Audio
You will need:
• Sequencer Software (Smart Score)
• A Sound synthesizer which converts
electrical signals into sound ( built
into PC sound board, an add on for
MAC)
• MIDI keyboard or device
• Ability to play the piano and music
theory background
• or a hired “expert”

16. MIDI
• A MIDI file is a list of commands that
are recordings of musical actions,
that when sent to a MIDI player
results in sound
• MIDI data is device dependent
• MIDI represents musical instruments
and is not easily used to playback
spoken dialog

17. MIDI Audio
• MIDI is a shorthand representation of
music stored in numeric form.
• Since they are small, MIDI files embedded
in web pages load and play promptly.
• Length of a MIDI file can be changed
without affecting the pitch of the music or
degrading audio quality.
• Working with MIDI requires knowledge of
music theory.

18. Digital Audio
• Digital audio is a representation
of the original sound
• Sampling rate is measured in
kilohertz (kHz)
Click to play

19. Digital Audio
• Digital audio represents a sound
stored in thousands of numbers or
samples.
• Digital data represents the loudness
at discrete slices of time.
• It is NOT device dependent and
should sound the same each time it
is played
• It is used for music CD’s

20. Digital Audio
• The three sampling frequencies most often
used in multimedia are CD-quality 44.1
kHz, 22.05 kHz and 11.025 kHz.
• The number of bits used to describe the
amplitude of sound wave when sampled,
determines the sample size.
• Digital audio is device independent.
• The value of each sample is rounded off to
the nearest integer (quantization).

21. Preparing Digital Audio
• Balance file size versus
quality
• Set recording levels
• Edit the recording

22. Preparing Digital Audio
• Balance file size versus quality
 To calculate file size in bytes:
Mono: sampling rate × duration of recording
in seconds × (bit resolution ÷ 8) × 1
Stereo: sampling rate × duration of recording
in seconds × (bit resolution ÷ 8) × 2

23. Digital Audio Editing
• Once a recording had been completed, it
almost always needs to be edited.
• Basic sound editing operations include:
trimming, splicing and assembly, volume
adjustments and working on multiple
tracks.

24. Digital Audio Editing
Additional available sound editing
operations include format conversion,
resampling or downsampling, fade-ins and
fade-outs, equalization, time stretching,
digital signal processing, and reversing
sounds.

25. MIDI vs. Digital Audio
• MIDI data and digital audio are like
vector and bitmapped graphics:
• Digital audio like bitmapped image –
samples original to create a copy
• MIDI – like vector graphic- stores
numeric data to recreate sound

26. MIDI vs. Digital Audio
• MIDI data is device dependent;
digital audio is not
• MIDI sounds (like vector graphics)
are different on different devices;
• Digital sounds are identical even on
different computers or devices.

27. MIDI Advantages
• MIDI file are much more compact and
take up less memory and system
resources
• MIDI files embedded in web pages
load and play much faster than digital
• You can change the length of a MIDI
file by varying its tempo
• With high quality MIDI devices, MIDI
files may actually sound better than
digital

28. MIDI Disadvantages
• MIDI represents musical instruments
not sounds and will be accurate only
if your playback device is identical
to the production device
• MIDI sound is inconsistent
• MIDI cannot be easily used to
reproduce speech

29. Digital Audio Advantages
• Digital audio sound is consistent and
device independent
• A wide selection of software support
is available for both MAC and PC
• A knowledge of music theory is not
required for creating digital audio,
but usually is needed for MIDI
production

30. Choose MIDI data
• If you don’t have enough RAM
memory, or bandwidth for digital
audio
• If you have a high quality sound
source
• If you have complete control over the
playback hardware
• If you don’t need spoken dialog

31. Choose Digital Audio
• If you don’t have control over the
playback hardware
• If you have the computing resources
and bandwidth to handle the larger
digital files
• If you need spoken dialog

32. Digital Audio
• You can digitize sound from a
microphone, synthesizer, tape
recording TV broadcast, or CD’s.
• Digitized sound is sampled every nth
of a second. The more often you take
the sample, the better the sound.
• Sample sizes are either 8 or 16 bits
and common frequencies are11.025,
22.05, and 44.1 kHz (See pp. 209-
211)

33. Digital Audio
• To prepare digital audio from analog
media, record it from a device, like a
tape recorder, into your computer
using digitizing software.
• Balance the sound quality with your
available RAM
• Set proper recording levels for a
good clear recording

34. File Size vs. Quality
• Audio resolution determines the
accuracy with which a sound is
digitized. (More bits in the sample
size produces better quality and
larger files)
• Stereo recordings are more realistic
and require twice as much storage
space and playback time.
• Mono files tend to sound “flat”

35. Editing Digital Recordings
• Apple’s QuickTime Player Pro
provides for primitive playback and
editing
• Sonic Foundry’s Sound Forge is a
more serious sound editor
• These can be used to trim, splice,
volume adjustment and format
conversion as well as special effects

36. Audio File Formats
• A sound file’s format is a recognized
methodology for organizing data bits of
digitized sound into a data file.
• On the Macintosh, digitized sounds may
be stored as data files, resources, or
applications such as AIFF or AIFC.
• In Windows, digitized sounds are usually
stored as WAV files.
• Both can use MIDI files (.mid)

37. Audio File Formats
• CD-ROM/XA (Extended Architecture)
format enabled several recording
sessions to be placed on a single
CD-R (recordable) disc.
• Linear Pulse Code Modulation is
used for Red Book Audio data files
on consumer-grade music CDs.

38. Sound for the World Wide Web
• To play MIDI sound on the web
– wait for the entire file to download and
play it with a helper application
– stream the file, storing it in the buffer and
playing it while it downloads
• Streaming is dependent on the
connection speed
• FLASH allows sound to be integrated
in a multimedia presentation,
controlled by buttons and saved as
.mp3

39. Adding Sound to a
Multimedia Project
• Decide what sounds you will need and
include them in the story board or cue
sheet.
• Decide whether to use MIDI or digital
audio
• Acquire source material (record/buy)
• Edit the sounds
• Test the sounds to be sure they are
timed properly

40. Adding sound to Multimedia
• CD- quality audio
Standard is ISO 10149, a.k.a. the “Red Book Standard”
Sample size is 16-bit
Sample rate is 44.1 kHz
11 seconds of audio uses 1.94 MB of space

41. Professional Sound
• The Red Book Standard- ISO 10149
– ( 16 bits at 44.1 kHz) allows accurate
reproduction of all sounds humans can
hear
– Software such as Toast and CD-Creator
can translate digital files from CD’s
directly into a digital sound editing file
or decompress.mp3 files into CD-Audio

42. Professional Sound
• Compression techniques reduce space but
reliability suffers.
• Space can be conserved by downsampling
or reducing the number of sample slices
taken per second.
• File size of digital recording (in bytes) =
sampling rate X duration of recording (in
secs) X (bit resolution/8) X number of
tracks.

43. Advanced Sound Management
• Scripting Languages such as Open
Script (Toolbook), LINGO(Director),
or Action Script ( FLASH) provide
better control over audio playback
• Requires some programming
knowledge

44. Production Tips
• Vaughn’s Law of Minimums - there is
an acceptable level of adequacy that
will satisfy the audience;
• If your handheld microphone is good
enough to satisfy you and your
audience, conserve your money and
energy.

45. Production Tips
• Recording on inexpensive media
rather than directly to disk
prevents the hard disk from being
overloaded with unnecessary data.
• The equipment and standards
used for the project must be in
accordance with the requirements.
• Sound and image synchronization
must be tested at regular intervals

46. Production Tips
• Audio recording - use CD’s, or VCR
tapes, or DAT ( digital audio tape)
tapes
• Create a good database to organize
your sounds, noting the counter and
content
• Testing and Evaluating- (delaying a
fast machine if needed to sync with
animation)

47. Production Tips
• Copyright Issues
• Securing permission for the use of
sounds and music is the same as for
images
• Can buy royalty-free digitized sound
clips
• DO NOT use someone’s original
work without permission!

48. Summary
• Vibrations in air create waves of pressure
that are perceived as sound.
• Multimedia system sound is digitally
recorded audio or MIDI (Musical
Instrumental Digital Interface) music.
• Digital audio data is the actual
representation of a sound, stored in the
form of samples.

49. Summary
• MIDI is a shorthand representation of
music stored in numeric form.
• Digital audio provides consistent playback
quality.
• MIDI files are much smaller than digitized
audio.
• MIDI is device dependent digital audio is
not
• MIDI files sound better than digital audio
files when played on high-quality MIDI
device.