Transcript Chapter 14:Recording and Editing Sound

Chapter 14
Recording and Editing Sound
Getting Started
• FAQs:
− How does audio capability enhance my PC?
− How does your PC record, store, and play digital audio?
− What do I need to know about converting music files?
− What should I know about MIDI?
− How do computers recognize and generate speech?
Practical PC 6th Edition Chapter 14
2
How does audio capability
enhance by PC
• Sound adds a new dimension to your computing experience
– Beeps and sound effects provide feedback as you use your PC
– Music lovers can listen to sample tracks
– Children can listen to stories
– Visually impaired individuals can have the screen contents
read to them
• Computers work with two general categories of sound
– Digital audio is a recording of real sound converted into
electronic signals
– Synthesized sound has not been recorded from a live source,
but instead has been generated by a machine
• Each sound category has unique characteristics and applications
Practical PC 6th Edition Chapter 14
3
How does audio capability
enhance by PC
Practical PC 6th Edition Chapter 14
4
How does my PC record, store, and
play digital audio?
• To digitally capture sound, you need a microphone and sound
software
• A sound wave provides information about a sound
– Height of wave indicates volume, called amplitude
– Time between wave peaks indicates the sound’s frequency
• To digitally store a sound wave, your PC periodically records a
sample of the wave’s amplitude as a binary number
– Sampling rates are measured in kHz (kilohertz), where 1
kHz is 1,000 samples per second
– For human speech, 11 kHz works fairly well. For music, 22
kHz to 44 kHz is required
– Digital sound files that have not been compressed are big
– Wave is a popular uncompressed audio file format
Practical PC 6th Edition Chapter 14
5
How does my PC record, store, and
play digital audio?
Practical PC 6th Edition Chapter 14
6
What do I need to know about
converting music files?
• Ripping is slang for importing tracks from a CD or DVD to your
computer’s hard disk
– Technical term for ripping is digital audio extraction
– Ripping is handy when moving files between PCs and devices
• Music file formats
– CD-DA (Compact Disc Digital Audio) format for music on CDs
– Music from CDs is usually compressed into: MP3, AAC
(Advanced Audio Coding), and WMA (Windows Media
Audio)
• Many software tools for ripping CD tracks are available
• In the U.S., ripping music for personal use is controversial
Practical PC 6th Edition Chapter 14
7
What do I need to know about
converting music files?
Practical PC 6th Edition Chapter 14
8
What should I know about MIDI?
• MIDI (musical instrumental digital interface) specifies a
standard way to store music data
– MIDI files contain instructions, called MIDI messages, for
synthesizing music based on pitch, volume, and duration
of each note made by each instrument
– MIDI is suitable for instrumental music, but not for vocals
– MIDI’s advantage lies in its ability to store lengthy musical
sequences in a small file
• Use sequencer software to capture the musical themes from
a MIDI instrument or enter the notes on a musical staff
• Edit your composition by assigning notes to instruments,
adding harmony, and inserting a percussion track
Practical PC 6th Edition Chapter 14
9
What should I know about MIDI?
Practical PC 6th Edition Chapter 14
10
How do computers recognize and
generate speech?
• Computers produce sound that resembles the spoken word
through speech synthesis
– Most speech synthesizers string together basic sound units
called phonemes
• Speech synthesis system typically includes text-to-speech
software and synthesizing hardware
– Text-to-speech software examines the text on a PC and breaks
it down into a series of sounds that can produce output
– Synthesizing software consists of electronic circuitry that can
generate speech or musical sounds
• Unlike digitized speech, synthesized speech can theoretically
produce any words or phrases
Practical PC 6th Edition Chapter 14
11
How do computers recognize and
generate speech?
Practical PC 6th Edition Chapter 14
12
Hardware: Audio devices
• Your computer’s sound card is responsible for transforming
the bits stored in an audio file into sound
– Expansion cards
– Integrated audio
• Basic audio circuitry is sufficient for most home and small
business use
• A digital signal processor transforms digital bits into analog
waves and vice versa, and handles compression and
decompression
Practical PC 6th Edition Chapter 14
13
Hardware: Audio devices
Practical PC 6th Edition Chapter 14
14
Hardware: Audio devices
• Your PC outputs sound to speakers or headphones
• The bundled microphone might be suitable for radio-quality
voice recording and sound effects
– Shop for a better-quality microphone for multimedia or
professional audio projects
• External speakers should be used for adequate volume
– 2.1 system
– 5.1 system
• Some speakers draw power from the computer
Practical PC 6th Edition Chapter 14
15
Hardware: Audio devices
Practical PC 6th Edition Chapter 14
16
Hardware: Audio devices
• Portable audio player
– Pocket-sized, battery-powered device that stores digital
music
– Transfer music from your PC or buy songs online
– Connect to earbuds, headphones, or car or home stereo
system
– Supports a variety of compressed audio formats
– Some can also play videos and e-books
• Rhythm and music activities are becoming increasingly
popular
Practical PC 6th Edition Chapter 14
17
Hardware: Audio devices
Practical PC 6th Edition Chapter 14
18
Can I copy it?
• What do you think?
– When you purchase a music CD, do you believe that you
have the right to convert it into any format (such as WMA
or MP3) for your own use?
– Do you think the Digital Millennium Copyright Act should
be revised to allow people to circumvent DRM for music
that has been purchased legitimately?
– Have you ever been prevented from copying music by
some type of DRM technology?
Practical PC 6th Edition Chapter 14
19