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Sound - PowerPoint PPT Presentation

pahana
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Sound

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  1. Sound

  2. Sound Capture • We capture, or record, sound by a process called sampling: “measuring” the sound some number of times per second. • Sampling rate is measured in KHz; 11 KHz to 128 KHz • Let’s see a simple example

  3. Sound wave Time

  4. Sample points Sound wave Time

  5. Sample points Sound wave Time

  6. Sample points Sound wave Time

  7. Sound wave How the sound would play back or output Time

  8. Sound Characteristics • Loudness (amplitude) • Tone, high or low (frequency) • Instrument (timbre) • Quality of sound is in the bit depth – much like color quality in video • 2^8=256 characteristics, 2^16=65,536 characteristics • Single track (monoral) or two (stereo) • CD quality is 44KHz, 16-bit, stereo

  9. Sound Formats • Pulse Code Modulation (PCM) – developed for phone calls and now called .WAV file type • Great for sounds, voice and music – but very big files: 4-minute song=40+ MB • Since we can’t hear all that 44MHz, 16-bit can give us, we compress the file using CODECs: MP3 for example; reduced using a bit rate (28-320Kbps, 128 is CD)

  10. Playing Sounds - MIDI • Musical Instrument Digital Interface • Hardware dependent – on sound card • Very small files; works for music not voice • FM Synthesis: electronic emulation of sound – sounds “electronic” • Wave Table Synthesis: recording of actual instrument samples that are “bent” for tone and timing. Polyphony = number of instruments; 64 to 256.

  11. The Right Sound Card • Always first: What are you going to use it for? • Low-end sound cards lean on processor for much of the work • 5.1 means five speakers and subwoofer • Recording signal to noise ratio; 40 is poor, 100 is good • Connectors: (Green) speakers; (blue) line out; (Pink) microphone; joy stick (15-pin female DB); Michael got it wrong bottom of page 801 • DirectX compatible: Version 9 (or 10?)

  12. Audio Cables • Used to come with sound card and often proprietary connector(s) • Cable now comes with optical drive, not sound card

  13. SPDIF • Sony/Philips Digital Interface connector • Sound card to 5.1 speaker system • Could be “Digital Out”

  14. Speakers • 2 = Stereo; left and right channels • 2.1 = Stereo plus woofer; probable best bet. • 5.1 = Six speakers total. Front Left, Front Right, Front center, rear left, rear right and woofer • 6.1 and 7.1 systems are now available

  15. Positional Audio • Uses 5+.1 system to place sound anywhere in 3-D space. Introduced with DirectX-3. • Creative Labs added to -3 with Environmental Audio Extensions (EAX); rolled into DirectX-8 in 2000 • Dolby Lab’s Dolby Digital used by DVDs, DTS (Digital Theater Systems) use 5.1

  16. On board sound • If sound is on the motherboard, make sure CMOS has it turned on. • You will find the sound driver(s) on the motherboard CD • Card goes into slot (or enabled in CMOS) first, then load drivers • Make sure connections to speakers is good

  17. Installing a Sound Card Drivers, drivers and more drivers DOS Support MIDI support WAV support Joystick support

  18. Troubleshooting • Always make sure the volume is turned up • Make sure you have good connections • Make sure speakers are on – they need power • Driver problems in Device Manager