Chapter 15 Recording and Editing Sound

2Practical PC 5 th Edition Chapter 15 Getting Started In this Chapter, you will learn: − How sound capability enhances your PC − How your PC records, stores, and plays digital sound − How speech synthesis works − What you should know about MIDI − What is ripping − About Hardware: Sound devices

3Practical PC 5 th Edition Chapter 15 How does sound capability enhance by PC Sound adds a new dimension to your PC – Beeps and sounds 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 – Digitized sound 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

4Practical PC 5 th Edition Chapter 15 How does my PC record, store, and play digital sound? 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 voice, 11 kHz works fairly well. For music, 22 kHz to 44 kHz is required – Digital sound files that have not been compressed are big – WAV is a popular uncompressed audio file format

5Practical PC 5 th Edition Chapter 15 How does speech synthesis work? Machines produce sound that resembles the spoken word through speech synthesis – Most speech synthesizers string together basic sounds called phonemes Speech synthesizer 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 be 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

6Practical PC 5 th Edition Chapter 15 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 percussion

7Practical PC 5 th Edition Chapter 15 What should I know about MIDI? Composing MIDI Music

8Practical PC 5 th Edition Chapter 15 What is ripping? 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 since it is done without the artist’s permission

9Practical PC 5 th Edition Chapter 15 What is ripping? Ripping music to a CD using iTunes software

10Practical PC 5 th Edition Chapter 15 Hardware: Sound devices Most PCs today include a basic audio system with a sound card, speakers, and possibly a microphone A sound card is a circuit board that typically plugs into an expansion slot on your PC − Provides connectors for a microphone, speakers or headphones − Provides a joystick port that doubles as a port for MIDI instruments Basic sound card is adequate for playing games, business software, and Web browsing

11Practical PC 5 th Edition Chapter 15 Hardware: Sound devices The sound card is the basic building block of your PC’s audio system

12Practical PC 5 th Edition Chapter 15 Hardware: Sound devices Digitized sound − Sound card reproduces the digital samples in the sound file − Sound quality depends on several factors, the most basic being frequency response. Frequency response is the range of notes it can produce MIDI music − Sound card receives messages from a MIDI file − Wavetable synthesis generates music by patching together a set of sounds (patch set) prerecorded as individual notes from actual instruments − 256-voice wavetable produces better quality sound than a 64-voice wavetable

13Practical PC 5 th Edition Chapter 15 Hardware: Sound devices Sound card outputs sound to speakers or headphones − New technologies include surround sound, 3-D sound, and environmental sound Speakers − Speakers cannot improve sound quality, but cheap speakers can degrade it − Your speaker quality level should match the quality level of your sound card − Most speaker systems include two speaker units − Higher end systems may also include a subwoofer to produce enhanced bass sound

14Practical PC 5 th Edition Chapter 15 Hardware: Sound devices Microphones − Sound card receives input from a microphone or MIDI device − For better sound quality choose a good-quality “mic” Portable audio player − Pocket-sized, battery-powered device that stores digital music − Transfer music from your PC or buy songs online − Connect to headphones or stereo system − Supports a variety of compressed audio formats − Some can also play videos and e-books

15Practical PC 5 th Edition Chapter 15 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 cassette tape 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?

16Practical PC 5 th Edition Chapter 15 Chapter Summary You should now : − Know how sound capability enhances your PC − Know how your PC records, stores, and plays digital sound − Understand how speech synthesis works − Know about MIDI − Understand ripping − Understand sound devices