Fundamentals of Audio Production. Chapter 6. 1 Fundamentals of Audio Production Chapter Six: Recording, Storing, and Playback of Sound.

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Fundamentals of Audio Fundamentals of Audio ProductionProduction

Chapter Six:Chapter Six:

Recording, Storing, and Playback Recording, Storing, and Playback of Soundof Sound

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Mechanical storage• The phonograph – cylinder recorder/player

developed by Thomas Edison.

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Mechanical storage• Gramophone – Emil Berliner’s disk-based

mechanical recorder

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Mechanical storage

• Modern record cutting lathes use electromagnetic heads to convert audio current into physical vibrations

• The vibrating stylus is heated to easily cut a groove in the vinyl disk

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Mechanical storage

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Mechanical storage

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Mechanical storage

• Modern phonographs use electromagnetic transducers called cartridges

• Cartridges convert physical energy which is stored in the grooves of the recording into electrical energy

• The stylus follows the undulating groove

• Movements of the stylus, vibrate a small magnet/coil mechanism

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Mechanical storage

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Magnetic tape recording

• Magnetic recording heads are transducers that convert electrical energy into magnetic

• Recording heads are electromagnets

• Audio current creates an alternating magnetic field

• The magnetic field is focused at the “gap” in the record head

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Magnetic tape recording

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Magnetic tape recording

• The fluctuations in the magnetic field are stored on tape by re-arranging the magnetic polarity of the “metal” surface of the tape

• The tape surface is made from powdered metals, like FeO2, or iron oxide (rust)

• The metals are attached to a plastic backing with binder (glue)

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Magnetic tape recording

• Playback heads are constructed in a nearly identical manner

• During playback, a current is induced to flow in the coil of the head by the magnetic charges of the tape surface

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Analog tape recording

• The paths on the tape where audio is recorded are called “tracks”

• The inputs on the recorder are called “channels”

• Stereo formats are two channel, but may be two or four tracks

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Analog tape recording

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Analog tape recording

• Tape width and track spacing affect cross talk between tracks

• Tape speed affects fidelity – Higher tape speeds produce greater signal-to-

noise ratios– Higher tape speeds produce wider frequency

responses

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Analog tape recordingThe Philips compact cassette

and track configuration

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Analog tape recordingReel to reel

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Analog tape recordingReel to reel

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Analog tape recordingCartridges

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Analog tape recording

• Commonalities across tape platforms

– Head arrangements• Erase, record, reproduce

– Capstan and pinch rollers pull the tape

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Analog tape recording

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Digital tape recording

• Digital audio tape stores binary data (on/off) represented by short bursts of electrical current

• Stationary head systems (DASH) use reel-to-reel tape transports

• DAT systems use helical scanning rotating head

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Digital tape recording

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Optical storage

• Electrical energy is converted into light energy by a LASER

• The LASER burns microscopic pits into the surface of a glass disk

• Binary data (on/off) triggers the LASER

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Optical storage

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Optical storage

• Compact disks are read by a LASER

• Light is refracted into a photoreceptor by “bumps” on the surface of the disk

• Each pulse of light is equal to an “on” state

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Optical storage

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Optical storage

• The pits made by the LASER are .5 microns wide and up to 3.5 microns in length

• How big is that?

• http://www.cellsalive.com/howbig.htm

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Solid state storage

• “Flash” memory is constructed from layers of layers of conductive and non-conductive materials

• The layers function as transistors

• Current is passed through the device’s thousands of transistors

• If it passes through, it represents an “on” in binary code

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Solid state storage

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Solid state storage

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Discussion

• What are the relative advantages and disadvantages of

– Mechanical– Magnetic– Optical– Solid state