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Digital Audio

Digital Audio. The mini series. Digital Audio Definition.

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Digital Audio

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  1. Digital Audio • The mini series...

  2. Digital Audio Definition • A sequence of discrete samples taken from a continuous sound (audio) waveform. Tens of thousands of samples are taken each second. Each sample represents the intensity of the sound pressure wave at that instant. Apart from the sampling frequency, the other parameter is the digital encoding of each sample including the number of bits used. The encoding may be linear, logarithmic or mu-law. • Digital audio is typically created by taking 16-bit samples over a spectrum of 44.1 thousand cycles per second (kHz), this means that CD quality sound requires 1.4 million bits of data per second. Digital telephone systems use lower sample rates.

  3. History of digital audio • 1877 the phonograph is born (by Thomas Alva Edison) • 1878 first music put on record: Yankee Doodle • 1888 Edison introduces the motor-driven phonograph • 1901 Experimental optical recordings are made on motion picture film. • 1910 Enrico Caruso is heard in the first live broadcast from the Metropolitan Opera, NYC

  4. History of digital audio • 1913 The first “talking movie” is demonstrated by Edison using his Kinetophone process, a cylinder player mechanically synchronized to a film projector. • 1919 the Radio Corporation of America (RCA) is founded. • 1925 The first electrically recorded 78 rpm disks appear. RCA works on the development of the ribbon microphone. • 1928 Dr. Georg Neumann founds a company in Germany to manufacture his condenser microphone.

  5. History of digital audio • 1932 The first cardioid ribbon microphone is patented by Dr. Harry F. Olson of RCE, using a field coil instead of a permanent magnet. • 1936 Von Braunmuhl and Weber apply for a patent on the cardioid condenser microphone. • 1940 Walt Disney’s “Fantasia” is released with eight-track stereophonic sound. • 1947 Ampex produces its first tape recorder, the Model 200

  6. History of digital audio • 1948 The Audio Engineering Society (AES) is formed in New York City. • 1949 RCA introduces the microgroove 45 rpm, large-hole, 7in record and record changer adaptor. • 1954 The first commercial 2-track stereo tapes are released. • 1956 Les Paul makes the first 8-track recordings • 1963 The Beach Boys contract Sunn Electronics to build the first large full-range sound system for their rock music concert tour.

  7. History of digital audio • 1969 Bill Hanley and Company designs and builds the sound system for the Woodstock Music Festival. • 1975 Digital Tape recording begins to take hold in professional audio studios. • 1980 Sony introduces a palm-sized stereo cassette tape player called a walkman. • 1981 Philips demonstrates the Compact Disc (CD) • 1982 Sony released the first CD player

  8. History of digital audio • 1984 The Apple Corporation markets the macintosh computer. • 1991 Apple debuts the “QuickTime” multimedia format. • 1992 The Philips DCC and Sony’s MiniDisc, using digital audio data-reduction, are offered to consumers as record/play hardware and software. • 1996 Record labels begin to add multimedia files to new releases, calling them “enhanced CDs.” • 1998 MP-3 Players for downloaded Internet audio appear.

  9. History of digital audio Phonograph Record Elec. Phonograph 78 RPM Ribbon Microphone Condenser Microphone Cardioid Ribbon Microphone Cardioid Condenser Microphone

  10. History of digital audio 2 track stereo 8 track stereo Tape recorder Woodstock Cassette Tape CompactDisc First CDPlayer Walkman

  11. History of digital audio 1st MacintoshComputer MiniDisc 1st MP3 Player

  12. DeterminingAudio File Size • Sample Rate: • The number of times per second a recording device samples sound waves, expressed in kilohertz (kHz). • a sample is a small fragment of sound waves. • it takes many samples to accurately reproduce sound. • the higher the sampling rate the higher the quality of audio.commercial CDs are recorded at 44.1 kilohertz (kHz) 44,100 samples per sec.

  13. DeterminingAudio File Size • Sample Size: • The number of bits of data in an audio sample: also called audio resolution. • The more bits the better the sound quality of the recording. • example: 16 bit sound file is a higher quality audio file then an 8 bit file.

  14. DeterminingAudio File Size • Number of Channels: • Monaural or Mono is a single channel audio. • Stereophonic or stereo has two channels of audio. • Surround sound has multiple channels (currently 5-7) • The more channels of audio the more realistic the sound and the larger the audio file.

  15. DeterminingAudio File Size • Time span of recording: • The Length of the Recording • The longer the length of the recording, the larger the file size.

  16. StreamingAudio • Streaming: • Streaming refers to the process of transmitting audio/video files, over the Internet, that can begin playing as the remaining data is temporarily transferring to your computer. • first developed by Real Audio. • user friendly because the audio can be listened to as the file is loading. • user does not have to wait for the completed file to load to begin hearing the audio.

  17. StreamingAudio • Compression: • a process used to reduce the size of a file. • the process can be lossless(no data permanently discarded during the compression) or Lossy(some audio data is discarded during the compression). • the lossless process provides full audio sound but can create a large file, causing problems with streaming. With lossy compression more data is lost as the compression increases

  18. StreamingAudio • Codec: stand for COmpression/DEcompress, software is used to compress the file before transmitting and to decompress it at the receiving end. • Transcoding: converts incompatible or obsolete data into a more suitable format. • Bandwidth: the rate of data transferred, in a given amount of time, over a network.

  19. Audio Scripts • PSA (Public Service Announcement)Announcements that inform the public about safety and health information, community services or public affairs. Much like a commercial but not for profit • Commercial: a paid advertisement or promotional announcement. • Plays: drama, comedy or mystery with a storyline/plot • Songs: a short metrical composition intended or adapted for singing

  20. Digital AudioEquipment • Computer and or mobile device: What will you be using? Mac, PC, Ipod, etc. (demonstrate Belkin tune talk on ipod). • Mixer/Audio Board: Look at handout 5.01.01. What items on an audio board will you need for your recording? • What microphone will you need? (mic info on next slide).

  21. Microphones • Condenser: microphone consisting of a capacitor with one plate fixed and the other forming the diaphragm moved by sound waves  • Dynamic: A microphone whose sound pickup device consists of a diaphragm that is attached to a movable coil • Piezoelectric:contain ceramic or quartz crystals linked with a diaphragm or directly exposed to acoustic waves. This arrangement reduces the electrical noise and output impedance • Wireless: is a microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated.

  22. Digital AudioEquipment • Speakers: electroacoustic device, often housed in a cabinet, that is connected as a component in an audio system, its function being to make speech or music audible. (surround sound, mono, etc.) • Headsets: a device consisting of one or two earphones with a headband for holding them over the ears and sometimes with a mouthpiece attached. (which kind will help you accomplish your objective?)

  23. Digital AudioEquipment • CABLES AND CONNECTORS

  24. Digital AudioEquipment • CABLES AND CONNECTORS

  25. Digital AudioEquipment • CABLES AND CONNECTORS

  26. MicrophonePIckup Patterns Unidirectional: A pick-up pattern which is more sensitive to sound arriving from one direction than from any other. Omnidirectional:Sound that comes from all directions Cardioid Hypercardioid

  27. MicrophonePIckup Patterns Bidirectional: will capture sound from the front and back of the diaphragm.

  28. MicrophonePIckup Patterns Shotgun: type of pickup pattern that is highly directional. captures sound in the direction the microphone is pointed. subject does not have to be in close proximity to the mic.

  29. AudioFile Formats • MP3: standard format for music file sent over the Internet. • WAV: standard for sound files on Microsoft & IBM PCs. Does not compress for audio as much as mp3 and other formats. • MIDI (Musical Instrument Digital Interface): format for recording music from electronic instruments.

  30. AudioFile Formats • AIFF (audio interchange file format): a common format for storing and transmitting sampled sound. The format was developed by Apple Computer and is the standard audio format for Macintosh computers • AAC (Advanced Audio Coding): standard audio file format for portable devices such as phones and gaming systems. • WMA (Windows Media Audio):Windows streaming audio file format. WMA files, which use the “.wma” file extension, can be of any size compressed to match many different connection speeds, or bandwidths.

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