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Sound on the Web
ata/index_sound_on_web.htm
•   Sound In Multimedia
•   Multimedia Sound Formats
•   What Format To Use
•   Adding Sound To Web Pages
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What is Sound?
 Identify what sound is
 Identify how sound works
 Understand what is meant by wavelengths,
frequency and amplitude
 Identify examples of sound levels

media_soundforge/02_Overview/CD_2.htm
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Introduction to Sound
 Sound is a longitudinal (back and forwards
movement along the direction travelled)
wave that can travel through gases (air),
liquids (under water) or solids (the Earth).
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Introduction to Sound
   Compressible waves have Wavelengths. The distance
between two areas of compression or rarefaction is the
wavelength. The number of waves that pass a certain
point in one second is the Frequency (measured in cycles
per second or Hertz (Hz))
   The size of the area of compression is similar to the
Amplitude. The Amplitude of the wave is measured from
the peak/trough to the midpoint.
   The intensity of sound waves
produce a sound pressure level,
which is commonly measured in a
unit, called the Decibel.
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Introduction to Sound
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Analogue and Digital
   Analogue signal will resemble the original speech or music by having the
frequency or amplitude of the wave go up and down in the same way as the
sound in speech or music goes up and down.
   The word analogue means similar or corresponding.
   Information in the form of an analogue signal can be added to another
electromagnetic wave, which is used for transmission. This wave carries the
analogue signal and is called the carrier wave. For much of the last century
information was transmitted in the form of analogue signals.

   Digital Signal uses a code with two states that are called on and off. The on
state is a small pulse of the electromagnetic wave. The off state is the gap in
between the pulses where there is no electromagnetic wave.
   When the digital signal reaches its destination the series of on and off states
must be changed back into the original information. This process is called
decoding.
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Analogue to Digital Conversion
 Devices exist which convert from analogue
signals to digital signals and vice-versa.
 Although most signals that we can perceive in the
real world are analogue (sound levels in speech,
light levels in vision etc.) more and more signals
are being stored in digital format (audio CDs,
DVDs, digital audio cassettes etc.)
 The problem with all signals is that they acquire
noise
 Noise is any unwanted change to a signal that
tends to corrupt it.
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Nyquist Thoery
ndforge/02_Overview/2_04/snd_sf7_004b.pdf?
 To reproduce a waveform you need to sample the variation of sound
at least twice every period of that waveform.
 In computer terms, the amplitude (or voltage) is measured in bits.
Every bit keeps the value of the amplitude (or voltage) as a binary
number. The more you have bits, the more you have values.

   When sound is converted from analogue into digital audio, the
hardware "samples" the level of the waveform at a specific interval.
For CD audio, this interval is 1/44,100th of a second.
   In other words, 44,100 times each second a special chip calculates a
value for analogue input and sends it off for use or storage. This
process is called "digitizing" a sound.
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Sample Rate
  In developing an audio sound for computers or
telecommunication, the sample rate is the number of
samples of a sound that are taken per second to
represent the event digitally.
 The more samples taken per second, the more accurate
the digital representation of the sound can be. For
example, the current sample rate for CD-quality audio is
 44,100 samples per second. This sample rate can
accurately reproduce the audio frequencies up to 20,500
hertz, covering the full range of human hearing.
media_soundforge/02_Overview/2_05/snd_sf7_005b.pd
f?
Sound Forge

Essentials
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What is Sound Forge?
 Sound Forge is an audio editor that
includes a powerful set of audio processes,
tools and effects for recording and
manipulating audio.
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Digital Trend
 Leisure has been revolutionised by Digital
Audio
• MP3
• MIDI

 Sound Forge allows user to extract and
record audio digitally
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What’s the Difference ?
 MIDI is note based
• played through an instrument

 Digital Audio – MP3
• Reproduction approximation of actual sound
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 Why Use Sound Forge?
 Case Study - Sound in the Film Industry
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Contents
   Tour of Sound Forge
– Audio files
– Workspace
– Data Window
   Working with Audio
– Preparing and Importing Source Clips
   Editing Audio

   Producing Final Audio
– CDROM / MP3
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Tour of Sound Forge
 Typical Procedure
•   Import of audio in digital format
•   Editing of audio with data window timeline
•   Producing a rough cut
•   Refinement and addition of effects
– Echo / pitch / volume
• Export of completed digital audio
Equipment Requirements and
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Features
   PC
• Sound Forge requires Microsoft DirectX Media
6.0 or later and Internet
• Explorer 4.0 or later.
   Sound Card
   Enhancements include:
• Sound Forge can open and save audio files with any of the
following bit depths:
–   • 8-bit
–   •16-bit
–   • 24-bit integer
–   • 32-bit float
   CD Ripping and MP3 output
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Tour of Sound Forge
 Key windows

• Timeline
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Tour of Sound Forge
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Play Bar
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Data Window
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Basic Editing
 Copying
audio
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Basic Editing
 Paste audio
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Trimming / Cropping Audio
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Zooming in
 Seeing more of the detail
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File Formats
 Sound Forge does not use a proprietary
format
• PC - .wav
– .avi Video for Windows
– .rm Real Media
– .raw
– Pulse Code Modulated
– A-Law / m-Law

• Mac - .aiff
.snd
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Recording Audio
   Prior to recording digital audio, you must
understand that the:
• Record and
• Record Remote dialogs
are destructive and contain no Undo capabilities.
 To avoid accidentally recording over valuable
audio data, all incoming audio should be
recorded into a new data window and
subsequently pasted into the desired data
window.
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Recording Audio
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Recording Audio in Remote Mode
   Clicking the Remote button places Sound Forge
into Remote Recording mode. In this mode, the
application’s workspace is hidden and replaced
with the Record Remote dialog. The Remote
Record dialog remains the topmost window
regardless of the number of open applications.
Remote recording is particularly useful when
using an application that controls the input
source, such as a mixer, CD audio, or MIDI
sequencing.
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Remote Mode
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Extracting data from CD
 Choose Extract Audio from CD from the
Tools menu. Sound Forge identifies the
system’s CD-ROM drive(s). If the system is
equipped with multiple CD-ROM drives, the
desired drive must be selected from the
Drive drop-down list.

 After the drive is selected, the Extract Audio
from CD dialog is displayed and all tracks
are listed.
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Extracting data from CD
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Writing Audio to CD
 Sample rates deviating from 44,100 Hz will
cause CD track lengths to be
miscalculated. When attempting to write a
file to CD that deviates from the 44,100 HZ
sample rate, Sound Forge will prompt you to
change the sample rate. Selecting Yes will
automatically resample audio to 44,100 Hz.
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 Drag-and-drop pasting
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Drag and Drop - Pasting
 Hold the ALT key and drag the selection to
the data window.
• A vertical dotted line representing the leading edge of the source
selection is displayed in the destination window.

• The letter “P” is
displayed in
the box
to the pointer.
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Drag and Drop - Mixing
   A shaded region representing the source selection is displayed in the
destination window.
   An “M” is displayed in the box adjacent to the pointer.
   Position the leading edge of the shaded region in the Tutor1 data
window where the mixing of the selection will begin.
   Release the mouse button. The Mix dialog is displayed.
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   Hold the Ctrl key and drag the selection to the destination
window.
   A shaded cross (or bowtie) region representing the
source selection is displayed in the destination window.
   A “C” is displayed in the box adjacent to the pointer.
   Align the right edge of the shaded region with the right
edge of the data in the destination window.
   Release the mouse button. The Crossfade dialog is
displayed.
   Specify the desired crossfade in the Name drop-down list
and click OK. The selection is crossfaded into the
destination data and the file is adjusted accordingly.
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Drag and Drop - New
 Drag the selection to an empty area of the
Sound Forge workspace and drop it. A new
data window containing the selection data
with the attributes of the original file is
created.
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Working with .avi Files
 Sound Forge supports opening and saving
Microsoft Audio and Video Interleave (AVI) files.
 Using Sound Forge, you can edit an AVI file’s audio
track with single-frame accuracy.
• the file may contain only one video stream and one
audio stream
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Working with .avi Files
   Frame animation
• When playing an AVI, you are able to specify if
frames are animated or displayed as still frames.
To turn on frame animation, right-click the video
strip and choose Animate from the shortcut menu.
A check mark is displayed adjacent to the
command to indicate this feature is turned on.
   Using the cursor to select a frame
• When Frame Animation is enabled, clicking
anywhere within the audio portion of the data
window displays the corresponding video frame in
the video strip. This is a convenient method of
viewing many individual frames, but does little to
achieve frame-accurate synchronisation.
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Working with .avi Files
   Video preview
• To view a larger version of the AVI, choose Video Preview
from the View menu during editing or playback. The current
frame is displayed in Video Preview window.
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Saving .avi files with added Audio
   Saving an AVI in Sound Forge is essentially a
three-step process that involves doing the
following:
• Specifying the audio and video streams to be saved.
• Compressing the video.
• Compressing the audio.

When using compression algorithms, you must strike a balance
between video quality, size reduction, and
compression/decompression processing time. Applying extreme
compression to video often results in visual artifacts, such as
jumpy or grainy video.
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MIDI
 For users that are capable of playing
musical instruments such a keyboards
• Notes + instrument
 Sound Forge can be used to capture
information – see Sound Forge Power !
Book by Scott R. Garrigus
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Cool Effects
   Changing Sample Rate and Bit Depth
   Echo
• Repeat sounds that mimic an initial sound
–   Simple delay – 0.001 to 5 seconds
–   Multi-tap delay – many simple delays at once
–   Chorus
–   Flange
   Pitch
• Bend
• Shift
   Volume
• Amplitude Modulation
• Distortation
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Changing Sample Rate and Bit Depth

undmultimedia_soundforge/06_FileAtts/6_02/s
nd_sf7_034b.pdf?
 If you selected a higher sample rate e.g. 48,000
you will have noticed that the pitch was higher
and the duration was shorter.
 If you selected a sample rate of 8,000 the pitch
would have been lower and the duration longer.
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Changing Sample Rate and Bit Depth

 To maximize storage space larger sound
files (24 and 16 bit) are frequently
converted to smaller (16 and 18 bit).
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Simple Delay
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Multi-tap Delay
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Chorus
 Produces a fuller sound
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Flange
 Produces a spacey, whoosh or warble
sound
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Pitch -Bend
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Pitch - Shift
 When the pitch is raised (lowered) it
shortens (lengthens) the data

 Shift stops this
side effect
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Amplitude Modulation
 Modifies the volume
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Distortion
 Allows user to add noise
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Sound Compression
dia/data/soundmultimedia_soundfo
rge/06_FileAtts/6_05/snd_sf7_037b.
pdf?
 Understand the difference between
• Lossy
– typically discarding data that is
calculated to be inaudible to the human
ear.
• lossless
– all the fidelity of the original source
   Identify the MP3 file format
   Examples of uncompressed audio
files
• WAV, AU, and AIFF.
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 The Volume Function
• Increase / Decrease the amplitude of the
selected data or the entire file
– Process > Volume

Too high and
clipping can occur
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   Process > Graphic

Envelope Points
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Normalise
   Process > Normalize
• Will remove clipping effect by checking the highest
amplitude first

Can normalise between two separate tracks
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Equalisation (EQ)
 Ability to adjust Treble and Bass
 Process >

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