introduction to multimedia unit 7 – multimedia element: sound 2014-15 semester 2

Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

Unit Unit 77 – – Multimedia Element: Multimedia Element: SoundSound

2014-15 2014-15 Semester 2Semester 2

Unit 7: Multimedia Element: SoundUnit 7: Multimedia Element: Sound

Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

2

Unit OutlineUnit Outline

• In this unit, we will learn– Use of Sound

– Guidelines for Using Sound

– Basic Principles of Sound

– Sound Quality• Sample Rate• Audio Resolution

– Digital Audio File Size

– Audio Compression

– Downloaded vs. Streamed

– Sound Card

– Digital Audio Software

– Media Players

– Audio File Formats


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

3

IntroductionIntroduction

• The element of sound can be important to achieve the goals of a multimedia product.

• Sound adds another dimension.• If used well, sound is an extremely powerful

element which can stimulate emotional responses that would never be activated from text and graphics alone.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

4

IntroductionIntroduction

• Sound helps convey the intended message or complement the purpose of multimedia applications.

• To help ensure effectiveness, it is important to incorporate sound files that are high quality, appropriate, and consistent with the goals of the multimedia product.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

5

Use of SoundUse of Sound

• Providing controls (such as skip, pause, mute, volume adjustment) is an effective way of keeping users involved and motivated.

• The decision to incorporate sound into a multimedia product should have solid reasoning behind it.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

6

Use of SoundUse of Sound

• Sounds are either content sounds or ambient sounds.

• Content sounds furnish information– Narration, dialogue are content sounds.– Music and other sounds can be considered as content

sounds if they are parts of the topic themselves.

• Ambient sounds reinforce messages and set the mood– Background sounds and special effects are ambient

sounds.– Special sound effects can reinforce or enliven a

message.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

Guidelines for Using SoundGuidelines for Using Sound

• Use the same style of music (if multiple sound files are needed) to maintain a sense of unity

• Coordinate sound files with other media elements

• Sound quality should be kept consistent• Record at a rate and resolution that is

appropriate to the delivery mode

7


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

Guidelines for Using SoundGuidelines for Using Sound

• Use the same voice for narration and voiceovers, but different voices for different characters

• Optimize files for background music• Use sound cues for specific events• During voice-overs, background music should

be turned off or adjusted to a low volume such that the spoken words can be understood without difficulty

8


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

9

Basic Principles of SoundBasic Principles of Sound

• When we speak, vibrations, called sound waves, are created.

• Sound waves have a recurring pattern or an analog wave pattern called a waveform.

This analog wave pattern represents the volume and frequency of a sound.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

10


• Amplitude: Distance between the valley and the peak of a waveform; determines volume

• Volume is measured in decibels (dB)– Decibel (dB) is a logarithmic unit used to describe a

ratio.– One dB is close to Just Noticeable Difference (JND)

for sound level.

• Frequency: Number of peaks that occur in one second measured by the distance between the peaks; determines pitch


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

11


• Analog sound is a continuous stream of sound waves. For sound to be included in multimedia applications, analog sound must be converted to digital form.

• Digitizing (or sound sampling): the process of converting analog sound to numbers

• Digital Audio: An analog sound that has been converted to numbers


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

12


Sound sampling converts analog sound to digital audio.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


• During digitizing, sound samples are taken at regular time instants.

• Time instants are discrete.• Sound samples (the volumes of sound at time

instants) cannot be stored precisely. Instead, only quantified values can be stored.

• The feasible quantified values are known as quantization levels.

13


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


• The number of quantization levels is related to the quality of digital audio.

• If more quantization levels are allowed, the difference between the original value and the quantified value will be smaller and we will get a better quality of the digital representation. However, this would also mean a higher cost for storage and processing of these values inside a computer (disks of larger capacity and more powerful CPUs are required)

14


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

15

Sound QualitySound Quality

• Factors that determine the sound quality of digital audio– sample rate– audio resolution

• Sample rate– Number of sound samples taken per second– Also known as sampling rate– Measured in kilohertz (kHz), – Common values: 11 kHz, 22 kHz, 44 kHz– CD quality: 44 kHz


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

16


• Audio resolution– Also known as sample size or bit resolution– Number of binary bits used to represent each sound

sample– As the audio resolution increases, the quality of the

digital audio also improves.– Audio resolution determines the accuracy with which

sound can be digitized.– Common values: 8 bits, 16 bits– CD quality: 16 bits


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


17

Audio Resolution Number of Quantization Levels

16-bit 216 65536 possible values for the sound sample





Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

18

Monophonic vs. Stereo SoundMonophonic vs. Stereo Sound

• Monophonic sounds: flat and unrealistic when compared to stereo sounds

• Stereo sounds: much more dynamic and lifelike• Monophonic sound files are sometimes a more

appropriate choice where storage and transfer time are major concerns.

• Narration and voiceovers can effectively be saved in a monophonic format.

• Music almost always must be recorded and saved in stereo.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

19

Digital Audio File SizeDigital Audio File Size

* Where number of channels, either 1 for monophonic or 2 for stereo

File size of a digital audio recording (in bytes)(assume that there is no compression)

File size of a monophonic digital audio recording (in bytes)(assume that there is no compression)

File size of a stereo digital audio recording (in bytes)(assume that there is no compression)


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

20

Audio CompressionAudio Compression

• Similar to image compression (refer to Unit 5), mathematical algorithms are used to reduce file sizes.

• File size is the primary consideration when using audio files on the Web.

• Compression is beneficial for storing and transferring audio files.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

21

Audio CompressionAudio Compression

• Different compression schemes are available for different file formats, and some file formats include the compression scheme within the format itself.

• The compression scheme applied impacts both the quality of audio file and the file size.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

Digital Audio File Size (Revisit)Digital Audio File Size (Revisit)

•

(Recall from Unit 5)

• Example: When a 6 MB audio file is compressed to 3 MB, the compression ratio is (6 / 3) = 2.

File size of a digital audio recording (in bytes)(assume that the compression ratio is CR)

22


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

23

Downloaded vs. StreamedDownloaded vs. Streamed

• Web audio: downloaded or streamed• Downloaded audio file must be entirely saved to

the user’s computer before it can be played.• Streaming: a more advanced process that

allows audio file to be played as it is downloading (i.e. before the entire file is transferred to the user’s computer)

• If we want our audio files to be streamed over the Internet, the web-hosting service must support streaming.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


• If the user’s computer receives streaming audio data more quickly than required, the excess data will be stored in a buffer.

• If the user’s computer receives streaming audio data slower than required, the data stored in the buffer will be used. If the buffer becomes empty, the user will experience a break.

24


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


• Two types of streamed audio:– On demand

• Streamed audio is stored on a server for a long period of time, and is available for transmission at a user’s request

– Live• Live streams are only available at one particular time

• Example: live radio programme

25


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

DeliveryDelivery

• To play sound on a computer system, a sound card and speakers, or a headset are needed.

• The digital audio file is sent through a digital-to-analog converter (DAC) so that it can be heard.

• It is important to test sounds under a variety of different conditions.

26


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

Sound CardSound Card

• Is an expansion board in a computer which interfaces with the processor through slots on the motherboard

• Can be integrated on the motherboard• Externally it is connected to speakers for

playback of sound• Main functions:

– Playback– Digitizing– Recording– Compressing

27


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


• Example: Creative Labs SoundBlaster

28


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


• Basic components of sound card:– Memory banks

• for storing audio data during digitization and playback of sound files

– DSP (Digital Signal Processor)• gives the sound card ability to perform functions like

digital filtering, anti-aliasing, noise shaping and compression

– DAC / ADC (Digital-to-Analog Converter, Analog-to-Digital Converter)

• for digitizing analog sound and reconverting digital sound files to analog form for playback

29

SSelf-elf-SS

tudy

tudy

SSlid

elid

e


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


– Input Ports: MIC, Line In• for feeding audio data to the sound card through a

microphone connected to it; for feeding audio data from external CD players for recording or playback

– Output Ports: Speakers, Line Out• for attaching speakers for playback of sound files; for

connecting to external recording devices or an external amplifier

– MIDI Input Port• for interfacing with an external synthesizer. Using this

connection, MIDI songs can be composed on the PC using software and then can be sent to the sound modules of external synthesizers for playback.

30

SSelf-elf-SS

tudy

tudy

SSlid

elid

e


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

31

Digital Audio SoftwareDigital Audio Software

• Traditional sound studio equipment is utilized to record, mix and edit audio. The cost can be tens of thousands of dollars.

• With sound editing and mixing software,audio files can be produced for muchless money.

Sound editing software is generally a much cheaper way to mix audio for a multimedia application than using traditional sound studio equipment.


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

32


• Examples:– Peak

• for Macintosh platform – Sound Forge

• for Windows platform

– Adobe Audition• for Windows platform

• formerly called Cool Edit


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


• Basic sound editing operations– Multiple tracks editing

• Edit and combine multiple tracks and then merge the tracks and export them in a “final mix” to a single audio file

– Trimming• Remove “dead air” or blank space from the front of a

recording and any unnecessary extra time off the end

– Splicing and assembly• Remove the extraneous noises that inevitably creep into

a recording

– Volume adjustments• Provide a consistent volume level

33

SSelf-elf-SS

tudy

tudy

SSlid

elid

e


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


– Format conversion• Import and save files in various formats

– Resampling or downsampling• Increase or reduce sample rates

– Fade-ins and fade-outs• Smooth out the very beginning and the very end of a

sound file

– Reversing sounds• Reverse all or a portion of a digital audio recording

34

SSelf-elf-SS

tudy

tudy

SSlid

elid

e


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

Media PlayersMedia Players

• Popular media players:– Windows Media Player– QuickTime Player– RealPlayer– iTunes

• Media players should:– be equipped to open and display most popular audio

file formats– possess the ability to play live

streaming audio

35


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

36

Audio File FormatsAudio File Formats

• MP3 (MPEG - Audio Layer 3)– Open standard technology – Uses file compression to create near-CD quality audio

files

• WAV (Waveform format)– for Windows platform

• Real formats (RA, RAM, RM)– for streaming audio

• WMA (Windows Media Audio)– Developed by Microsoft


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

37


• ASF (Advanced Systems Format)– Formerly known as Advanced Streaming Format– Mircosoft’s proprietary format for streaming– Stores audio and video information– Specially designed to run on networks– Content is delivered to users as continuous flow of

data; little waiting time will be experienced before playback begins

• AIFF or AIF (Audio Interchange File Format)– Macintosh waveform format


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia


• MIDI (Musical Instrument Digital Interface):– Internationally accepted file format for storing MIDI

data– Provides instructions on how to replay music; does not

record the waveform (MIDI data is not digital audio)– Files of MIDI format are often smaller than those of

most other audio file formats– If spoken dialog is needed, digital audio should be

used instead

38


Intr

odu

ctio

n t

o

Intr

odu

ctio

n t

o M

ult

imed

iaM

ult

imed

ia

ReferenceReference

• Part of this slide set is prepared or/and extracted from the following book:– Multimedia For The Web Revealed, Calleen Coorough

& Jim Shuman, Thomson Learning, 2006, ISBN:1-4188-3953-1

• This set of slides is for teaching purpose only.• Self-study slide(s) is / are within the scope of the

final examination.

39

introduction to multimedia unit 7 – multimedia element: sound 2014-15 semester 2

Documents

sound introduction

introduction sound

element of sound

sound waves

multimedia element

multimedia unit

use of sound sounds

use of sound guidelines