Digital Audio
Lesson Objectives
After completing this lesson, you will be able to:
 Identify the various characteristics of digital audio.
 Explain the concepts of recording, copying, and
converting digital audio.
 Identify the features of advanced speech
technologies.
Analog and Digital Audio
 When you speak, the sound you create is in the
analog or wave format.
 The sound that you hear is also in analog format.
 Computers are basically digital devices. Therefore,
it is necessary to convert audio from the analog format
to the digital format before using it on a computer.
Analog and Digital Audio (cont.)
 Digital audio technology allows you to record, edit,
and play digital audio files on a computer.
 Advanced digital audio technology also lets you
communicate with the computer by just speaking.
Characteristics of Digital Audio
 Digital Audio file can be compressed.
 Audio files are generally large.
 Compressed audio files save space, allow portability,
and are easier to transfer over the Internet.
 When you compress audio files, the quality of the audio
file is generally affected.
Characteristics of Digital Audio
(cont.)
 Another important characteristic of digital audio is
that it can be edited on a computer by using audio
editing software.
 You can use audio editing software to move
sections within an audio file or add effects.
 You can also use audio editing software to store an
audio file in different formats on the computer.
Audio File Formats
 Some of the common formats that you need to be
familiar with are:
 Wave (WAV)
 MPEG Audio Layer 3 (MP3)
 Windows Media® Audio (WMA)
Wave (WAV)
 This format is part of a series of standards for audio and
video developed for Microsoft Windows® 95 as a
universal sound file format.
 It is used to store audio files in the wave audio format.
 Audio files stored in this format have good audio quality.
 Audio files in this format are larger when compared with
other formats.
MPEG Audio Layer 3 (MP3)
 This format was developed by Motion Picture Expert
Group to allow compression of audio and video for digital
distribution.
 The MP3 format is a popular format that is used to store
digital audio files.
 MP3 files are generally smaller than WAV files.
Windows Media® Audio (WMA)
This format was developed by
Microsoft and is used to store
digital audio files.
Audio Streaming
 Digital audio allows streaming of digital audio files.
 You can use a streaming audio player or a browser plugin to play the audio file from the Internet.
 The audio file is sent to your computer in a continuous
stream.
Recording, Copying, and
Converting Digital Audio
 The technique of recording and storing audio files in a
digital format is called digital recording.
 You can then copy the stored audio files to storage
devices, such as recordable CDs and DVDs, in various
formats, such as WAV and MP3.
 You can also convert audio from a CD or a DVD to a
different format before you store it on your computer’s
hard disk.
Copying Audio
Hardware
 You can copy audio from storage devices, such as a
computer’s hard disk, and store it on a recordable CD or
DVD.
 This process of copying audio to a recordable CD or
DVD is referred to as burning.
 You need a special hardware device, such as a CD
writer or a DVD writer, to copy audio to recordable CDs
or DVDs.
 A CD writer allows you to copy audio only to recordable
CDs whereas most DVD writers allow you to copy audio
to recordable CDs and DVDs.
Copying Audio
Software
 Along with hardware, you also need software to copy
audio to a recordable CD or DVD.
 You can use the software to create different types of
CDs. You can create data CDs, audio CDs, and mixed
mode CDs.
 Mixed mode CDs contain audio, video, and data files.
Converting Audio
 You can convert audio from a CD or a DVD to a different
format before storing it on a computer’s hard disk.
 Example:
 You can convert your favorite song from a CD to an MP3 file
before storing it on the computer.
 You can then play the MP3 file by using the digital devices, such
as an MP3 player.
Converting Audio (cont.)
 You must have audio conversion software, such as
Microsoft Windows Media Player, installed on your
computer to convert audio files.
 The software changes the format of the audio and
might also compress the audio so that the files take up
less space on the hard disk.
 You can then transfer these audio files from the
computer to a portable medium, such as a PDA or a cell
phone.
Speech Recognition and Synthesis
 Digital audio technology allows you to interact with
the computer by just speaking.
 This helps improve productivity and empowers
challenged users to expand their ability to use
computers.
Speech Recognition
Speech Recognition
 Speech recognition is a technology that allows you to
communicate with a computer by using only your
voice to enter text and to issue commands.
 To enable speech recognition, you need an audio
input device, such as a microphone, a sound card,
and speech recognition software that converts human
speech into text or commands for the computer.
 You can use speech recognition technology to interact
with various programs
Speech Recognition (cont.)
 The speech recognition feature is readily available in
Microsoft Office XP applications such as Word.
 In Word, you can use the speech recognition feature to
dictate words, which are then converted to text.
 You can also select menus, toolbars, and dialog box
items.
Speech Synthesis
Speech Synthesis (cont.)
 Speech synthesis is a technology that allows the
computer to speak to you.
 In speech synthesis, the computer communicates to you
by converting text to digital audio.
 Windows XP has a built-in feature that supports speech
synthesis.
 To support speech synthesis, your computer must be
equipped with a sound card and speakers.
 To configure the speech synthesis options on your
computer, in Control Panel, double-click Speech.
Questions