Fundamentals of Audio Production. Chapter 6.

1

Fundamentals of Audio Fundamentals of Audio ProductionProduction

Chapter Six:Chapter Six:

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

Fundamentals of Audio Production. Chapter 6.

2

Mechanical storage• The phonograph – cylinder recorder/player

developed by Thomas Edison.

Fundamentals of Audio Production. Chapter 6.

3

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

mechanical recorder

Fundamentals of Audio Production. Chapter 6.

4

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

Fundamentals of Audio Production. Chapter 6.

5

Mechanical storage

Fundamentals of Audio Production. Chapter 6.

6

Mechanical storage

Fundamentals of Audio Production. Chapter 6.

7

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

Fundamentals of Audio Production. Chapter 6.

8

Mechanical storage

Fundamentals of Audio Production. Chapter 6.

9

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

Fundamentals of Audio Production. Chapter 6.

10

Magnetic tape recording

Fundamentals of Audio Production. Chapter 6.

11

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)

Fundamentals of Audio Production. Chapter 6.

12

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

Fundamentals of Audio Production. Chapter 6.

13

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

Fundamentals of Audio Production. Chapter 6.

14

Analog tape recording

Fundamentals of Audio Production. Chapter 6.

15

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

Fundamentals of Audio Production. Chapter 6.

16

Analog tape recordingThe Philips compact cassette

and track configuration

Fundamentals of Audio Production. Chapter 6.

17

Analog tape recordingReel to reel

Fundamentals of Audio Production. Chapter 6.

18

Analog tape recordingReel to reel

Fundamentals of Audio Production. Chapter 6.

19

Analog tape recordingCartridges

Fundamentals of Audio Production. Chapter 6.

20

Analog tape recording

• Commonalities across tape platforms

– Head arrangements• Erase, record, reproduce

– Capstan and pinch rollers pull the tape

Fundamentals of Audio Production. Chapter 6.

21

Analog tape recording

Fundamentals of Audio Production. Chapter 6.

22

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

Fundamentals of Audio Production. Chapter 6.

23

Digital tape recording

Fundamentals of Audio Production. Chapter 6.

24

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

Fundamentals of Audio Production. Chapter 6.

25

Optical storage

Fundamentals of Audio Production. Chapter 6.

26

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

Fundamentals of Audio Production. Chapter 6.

27

Optical storage

Fundamentals of Audio Production. Chapter 6.

28

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

Fundamentals of Audio Production. Chapter 6.

29

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

Fundamentals of Audio Production. Chapter 6.

30

Solid state storage

Fundamentals of Audio Production. Chapter 6.

31

Solid state storage

Fundamentals of Audio Production. Chapter 6.

32

Discussion

• What are the relative advantages and disadvantages of

– Mechanical– Magnetic– Optical– Solid state