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05 audio

  1. 1. ia Systems520251: Multimed Êส‹‹Çว¹น»ปÃรÐะ¡กÍอºบÁมÑัÅลµตÔิÁมÕีàเ´ดÕีÂย [àเÊสÕีÂย§ง] 6 ÊสÔิ§งËหÒา¤คÁม 2555 1
  2. 2. Agenda• Properties of sound• Analog audio• Digital audio• Audio file formats• Sound recording• Sound editing 2
  3. 3. Introduction• Audio is the reproduction of sound - important means of communication.• There are a number of advantages of using audio. • most obvious: interface for visual disabilities 3
  4. 4. Properties of Sound • Sound is a pressure wave created by successively vibrating matter back and forth. • The sound wave is in the form of a sine wave. 4
  5. 5. Frequency• The number of air pressure oscillations per second at a fixed point by a sound wave• Measured in Hertz (Hz) - number of waves per second• Audible range (human) = 20 Hz - 20 kHz • this is where the sensation of pitch originates 5
  6. 6. Frequency & PitchFrequency PitchFrequency Pitch 6
  7. 7. Wavelength• The distance between waves 7
  8. 8. Amplitude • The height of the wave • Measured in decibels (dB or dBA) 8
  9. 9. Intensity vs. Loudness• Amplitude can be thought of as the intensity of sound and is measurable.• Loudness of sound is a perception. • Sound can be perceived differently at the various frequencies (1 kHz-4 kHz is more sensitive than the lower and the higher) • Individuals also have different hearing capacities. What is loud to one person may not be loud to another, which why loudness is a perception and cannot be measured. 9
  10. 10. dBA Sound 10 Normal breathing 20 Whispering at 5 ft 30 Soft whispering 50 Rainfall 60 Normal conversation 110 Shouting in the ear 120 Thunder110-120 Rock concert 130 Air raid 180 Rocket launching from pad 10
  11. 11. Analog Audio• analog = the measurement of continuous change or movement over a period of time 11
  12. 12. Digital Audio• The reproduction of sound using digital information• The value of the signal is sampled at regular intervals by an analog-to-digital converter (ADC) 12
  13. 13. Basic Terminology & Properties of DA• Channels• Sampling rate• Bit depth• Quality and file size• Compression• Audio codecs 13
  14. 14. Channels Stereo e s se d l c om p r i le w i l An u n gi t a l f e o di e s i ze o f a s te r c e t h b e t w i n o f i le . mo Mono 14
  15. 15. Sampling Rate• ADC - the signal is sampled at regular intervals• The value of each sample is rounded to the nearest integer in a scale that varies according to the resolution of the signal 15
  16. 16. Sampling Rate• The accuracy the reproduction to the source depends on how often the sample is taken. 16
  17. 17. Common DA Sampling Rate 8,000 Hz telephone, adequate for human speech 22,050 Hz radio 32,000 Hz miniDV digital camcorder CD, commonly used with MPEG-1 audio 44,100 Hz (VCD, SVCD, MP3) digital sound used for digital TV, DVD, DAT, 48,000 Hz films and professional audio96,000 or 192,400 Hz DVD-audio and HD-DVD audio tracks 17
  18. 18. Bit Depth• The number of bits used to describe each of the samples taken from the sampling rate • the potential accuracy of a digital audio• Higher bit-depth audio will sound better than lower one 18
  19. 19. Quality & File Size• Make the highest level (if possible) ~ 16-bit 44kHz Stereo • this produces a large file size, however, high audio clarity• Chances to manipulate such file (to make it smaller) : • reduce the sampling rate • make it mono 19
  20. 20. 20
  21. 21. Compression Audio Quality “later editing”• Digital audio files can also be compressed to reduce Lossless file size WMA Lossy • MPEG-1 Audio layer-3 MP3 Real Audio (MP3) is a common “transmission” File Size 21
  22. 22. Audio Codecs • An audio codec is a piece of software (coder/decoder) or a driver that provides support for certain audio formats for certain system. codec x codec y ✘Audio codecs codec x ✔ 22
  23. 23. Audio File Formats• An audio file format is a container format for storing • WAV format data on a computer system. • Microsoft’s audio format • AIF format • also one of the mostthe common format on • developed by Apple Computer web • MP3 • supported by most web browsers • most widespread form of audio on the Internet • AU format • playable on various • one of theformat on the common most players web • created by Sun Microsystems 23
  24. 24. 24
  25. 25. MIDI Format• Musical Instrument Digital Interface (MIDI) is typically used to play music.• MIDI files contain a set of instruction that the computer sends to a sound card, synthesizer, or other device. • Such instructions (note and instrument description) describe how to play the sound, rather than recording an actual rendition of the sound. 25
  26. 26. 26
  27. 27. Sound Recording 27
  28. 28. 28
  29. 29. 29
  30. 30. Sound Editing• Audacity - it’s GNU GPL license, it’s free, it’s cross platform. • Tracks • Waveform display • Selection • Trim • Amplify • Pitch • and many more.... 30
  31. 31. Digital AudioTechnologies & Applications 31
  32. 32. Portable Music Players 32
  33. 33. Before Digital70s 33
  34. 34. CD on market (1982) D ig i t al! I t ’s 34
  35. 35. Not quite portable, is it? 35
  36. 36. Digital files?Compress ‘em ATRAC WMA CODECS MP3 Vorbis (OGG) AAC 36
  37. 37. Digital Audio Players1997 - MPMan 1998 - Rio PMP300 SaeHan Infomation Systems Diamond Multimedia Eiger Labs MPMAN F10 (1998) 32 MB Internal Memory 32 MB SmartMedia Memory Slot 37
  38. 38. Digital Audio Players 2000 - Creative NOMAD Jukebox Creative Labs 6 GB Harddisk $500 38
  39. 39. The Revolution October 2001 - 1st iPod Introducing 39
  40. 40. iPod Family 40
  41. 41. 41
  42. 42. 42
  43. 43. Get quick and instant access to Tune into all your favorite stations Watch supported 720p HD movies, Connect, update, and buy content Surf the web anytime, anywhereyour content with multi-touch with crystal-clear reception. With TV shows and videos in high wirelessly from Wi-Fi hot spots. you have a Wi-Fi connection.navigation. With a 3.3-inch screen an integrated HD Radio receiver, definition on your HDTV through Stream millions of songs over Wi- Enjoy your favorite websites with aand vivid 16:9 OLED display you can access a variety of HD the Zune HD & AV Dock (sold Fi directly to your Zune HD and full-featured web browser including(480x272 resolution), premium Radio stations at no additional separately). Or take them with you turn it into a portable digital tap-to-zoom technology, built-inentertainment is at your fingertips.* cost. Plus, tag the songs you like for premium entertainment on the jukebox. accelerometer, and touchscreen for later purchase. go. Additional dock and HDTV are QWERTY keyboard. required.* 43
  44. 44. 44
  45. 45. 45
  46. 46. iTunes+ iTunes Music Store 46
  47. 47. 47
  48. 48. Online Music Stores 48
  49. 49. 49
  50. 50. Podcast 50
  51. 51. 51
  52. 52. AudioBooks 52
  53. 53. 53
  54. 54. Text-to-Speech 54
  55. 55. สถิติผู้พิการ 2550 ที่มา: สํานักงานสถิติแห่งชาติ 55
  56. 56. DAISY (Digital Accessibility Information System) 56

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