MMT Audio

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Transcript

  • 1. Text Audio Image/Graphics Movie Animation
  • 2. Audio
  • 3. Agenda • Properties of sound • Analog audio • Digital audio • Audio file formats • Sound recording • Sound editing
  • 4. 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
  • 5. 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.
  • 6. 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
  • 7. Frequency & Pitch
  • 8. Frequency & Pitch Frequency Pitch
  • 9. Frequency & Pitch Frequency Pitch Frequency Pitch
  • 10. Frequency & Pitch Frequency Pitch Frequency Pitch
  • 11. Wavelength • The distance between waves
  • 12. Amplitude • The height of the wave • Measured in decibels (dB or dBA)
  • 13. 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.
  • 14. dBA Sound 10 Normal breathing 20 Whispering at 5 ft 30 Soft whispering 50 Rainfall 60 Normal conversation 110 Shouting in the ear 120 Thunder 110-120 Rock concert 130 Air raid 180 Rocket launching from pad
  • 15. Analog Audio • analog = the measurement of continuous change or movement over a period of time
  • 16. 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)
  • 17. Basic Terminology & Properties of DA • Channels • Sampling rate • Bit depth • Quality and file size • Compression • Audio codecs
  • 18. Channels Stereo Mono
  • 19. Channels Stereo re s s e d i l l p u n c om a l file w An it re o dig t h e s i ze o f s te e e t w ic o n o file . b am Mono
  • 20. 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
  • 21. Sampling Rate • The accuracy the reproduction to the source depends on how often the sample is taken.
  • 22. 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, 48,000 Hz DAT, films and professional audio 96,000 or 192,400 Hz DVD-audio and HD-DVD audio tracks
  • 23. 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
  • 24. 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
  • 25. Compression • Digital audio files can also be compressed to reduce file size • MPEG-1 Audio layer-3 (MP3) is a common
  • 26. Compression • Digital audio files can also be compressed to reduce file size • MPEG-1 Audio layer-3 (MP3) is a common
  • 27. Compression Audio Quality • Digital audio files can also be compressed to reduce file size • MPEG-1 Audio layer-3 (MP3) is a common
  • 28. Compression Audio Quality • Digital audio files can also be compressed to reduce file size • MPEG-1 Audio layer-3 (MP3) is a common
  • 29. Compression Audio Quality • Digital audio files can also be compressed to reduce file size • MPEG-1 Audio layer-3 (MP3) is a common File Size
  • 30. Compression Audio Quality • Digital audio files can also be compressed to Lossless reduce file size WMA • MPEG-1 Audio layer-3 (MP3) is a common File Size
  • 31. Compression Audio Quality • Digital audio files can also be compressed to Lossless reduce file size WMA Lossy • MPEG-1 Audio layer-3 MP3 Real Audio (MP3) is a common File Size
  • 32. Compression Audio Quality “later editing” • Digital audio files can also be compressed to Lossless reduce file size WMA Lossy • MPEG-1 Audio layer-3 MP3 Real Audio (MP3) is a common File Size
  • 33. Compression Audio Quality “later editing” • Digital audio files can also be compressed to Lossless reduce file size WMA Lossy • MPEG-1 Audio layer-3 MP3 Real Audio (MP3) is a common “transmission” File Size
  • 34. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system.
  • 35. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system.
  • 36. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. codec x
  • 37. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. codec x
  • 38. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. codec x
  • 39. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. codec y codec x
  • 40. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. codec y codec x
  • 41. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. ✘ codec y codec x
  • 42. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. ✘ codec y codec x codec x
  • 43. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. ✘ codec y codec x ✔ codec x
  • 44. Audio Codecs • An audio codec is a piece of (coder/decoder) software or a driver that provides support for certain audio formats for certain system. ✘ codec y codec x ✔ codec x Audio codecs
  • 45. Audio File Formats • • An audio file format is a WAV format container format for storing • data on a computer system. Microsoft’s audio format • AIF format • also one of the most • developed by Apple common format on Computer the web • • supported by most MP3 web browsers • most widespread • AU format form of audio on the Internet • one of the most • common format on playable on various the web players • created by Sun Microsystems
  • 46. 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.
  • 47. Sound Recording
  • 48. Sound Recording
  • 49. Sound Recording sound recorder (mic, tape recorder, MD, etc)
  • 50. Sound Recording sound recorder (mic, tape recorder, MD, etc)
  • 51. Sound Recording sound recorder (mic, tape recorder, MD, etc)
  • 52. 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....