Sound

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 Windows\Media directory
•MS Office includes additional sounds
•You can add your own sounds by
including them in the
Windows\Media 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.