educational technology

1. Audio Recordings
mechanical, magnetic,
optical, digital
DUROY, Ollie

2.  The phonograph – cylinder recorder/player
developed by Thomas Edison.
2

3.  Gramophone – Emil Berliner’s disk-based
mechanical recorder
3

4.  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
4

5. Fundamentals of Audio Production.
Chapter 6. 5

6. 6

7.  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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8. 8

9.  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
9

10. 10

11.  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
11

12. 12
Analog tape recording
• The paths on the tape where audio is
recorded are called “tracks”
• The inputs on the recorder are called
“channels”

13. 13
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

14. 14
Analog tape recording
The Philips compact cassette
and track configuration

15. 15
Analog tape recording
Reel to reel

17. 17

18. 18
Analog tape recording
Reel to reel

19. 19
Analog tape recording
Cartridges

20. 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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21. Optical storage
21

22. 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
22

23. Optical storage
23

24. 24
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

25. 25
Digital tape recording

26. Digital Recording
Digital audio began in the telephone industry,
where it was used to digitize telephone
conversations and, in effect, compress them
so that more conversations could be handled
on existing lines.

27. Digital Recording
In 1971, Heitaro Nakajima joined
Sony.
Nakajima thought that by using
digital technology, which had only
been used in computers and long-
distance telephone transmission,
the quality of recorded sound
could be improved.

28. Digital Tape
1976 - The first 16-bit digital recording in the US was
made at the Santa Fe Opera on a handmade
Soundstream digital tape recorder developed by Dr.
Thomas G. Stockham.
1987--Digital Audio Tape (DAT) recorders and
players were introduced.

29. Other Digital Devices
1997 - MP3.com was
founded in November by
Michael Robertson with
3,000 songs available for
free download. In the
next 12 months, it
became the #1 music
site on the Internet with
3 million hits monthly.

30. Digital Recording Studio
1998 - Jonell
Polansky
produced the
first 24-bit 48-
track digital
recording
session at
Ocean Way
on Nashville's
Music Row

31. Portable Digital Recorders
E.G., the Boss BR-8 is
an eight track digital
recorder. It was one of
the first to offer a built in
zip disk drive for easy
storage and transfer
with computers.

32. Really Portable
Recorders were once
the size of an entire
room. Now they fit in
your hand.
The recording quality
was once very poor.
Now they are nearly the
same quality as
professional studios.

33. Optical Recording and Communications 48
Advantages of Digital CommAdvantages of Digital Comm
 Freedom from noiseFreedom from noise
 Digital representation avoids information lossDigital representation avoids information loss
 Error correction ensures clean transfer ofError correction ensures clean transfer of
informationinformation
 High information densityHigh information density
 Optical density greatly exceeds electronic densityOptical density greatly exceeds electronic density
 Data compression is possibleData compression is possible