Fundamentals of Audio Production

1. Fundamentals of Audio Production Chapter Six: Recording, Storing, and Playback of 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 • By “shouting into the funnel,” a diaphragm at the small end would vibrate • A stylus attached to the diaphragm would vibrate and cut a groove into the cylinder or disk • On playback, the stylus would track through the groove, causing vibrations in the diaphragm, which echoed through the funnel Fundamentals of Audio Production. Chapter 6.

5. Mechanical storage • Modern record cutting lathes use electromagnetic heads to convert audio current into physical vibrations • The electromagnets respond to audio current by alternatively pushing/pulling the stylus • The vibrating stylus is heated to easily cut a groove in the vinyl disk Fundamentals of Audio Production. Chapter 6.

6. Mechanical storage Fundamentals of Audio Production. Chapter 6.

7. Mechanical storage Fundamentals of Audio Production. Chapter 6.

8. Mechanical storage • Modern phonographs use electromagnetic transducers called cartridges • Cartridges convert potential 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.

9. Mechanical storage Fundamentals of Audio Production. Chapter 6.

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

11. Magnetic tape recording Fundamentals of Audio Production. Chapter 6.

12. 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.

13. 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.

14. 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.

15. Analog tape recording Fundamentals of Audio Production. Chapter 6.

16. 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.

17. Analog tape recording The Philips compact cassette and track configuration Fundamentals of Audio Production. Chapter 6.

18. Analog tape recording Reel to reel Fundamentals of Audio Production. Chapter 6.

19. Analog tape recording Reel to reel Fundamentals of Audio Production. Chapter 6.

20. Analog tape recording Cartridges Fundamentals of Audio Production. Chapter 6.

21. Analog tape recording • Commonalities across tape platforms • Head arrangements • First erase, second record, and last reproduce • Capstan and pinch roller squeeze together and pull the tape Fundamentals of Audio Production. Chapter 6.

22. Analog tape recording Fundamentals of Audio Production. Chapter 6.

23. 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.

24. Digital tape recording Fundamentals of Audio Production. Chapter 6.

25. 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.

26. Optical storage Fundamentals of Audio Production. Chapter 6.

27. 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.

28. Optical storage Fundamentals of Audio Production. Chapter 6.

29. 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 • Data is stored redundantly on the disk to avoid destruction or obliteration by dirt Fundamentals of Audio Production. Chapter 6.

30. 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.

31. Solid state storage Fundamentals of Audio Production. Chapter 6.

32. Solid state storage Fundamentals of Audio Production. Chapter 6.

33. Discussion • What are the relative advantages and disadvantages of • Mechanical • Magnetic • Optical • Solid state Fundamentals of Audio Production. Chapter 6.