Overview of Recording

1. Overview of Recording November 2, 2007 Storage

2. A Very Quick Review (Survey) of Electricity and Magnetism Essential Information for recording devices. You have seen this before in HS or in a physics class. Storage

3. ELECTROSTATIC RUBBINGSThink about this stuff dead cat - - - + - + - - Storage

4. Forces Between Charges F F Q1 Q2 Storage

5. Coulomb’s Law – the math • The Unit of Charge is the Coulomb. • The constant k=9 x 109 N-m2/C2 • or k=9,000,000,000 N-m2/C2 • d is measured in meters. Storage

6. Electrical Charge • The negative charge is identified with electrons. • Electrons can be “pushed around” wired (circuits) with the use of a battery. • “Resistors” impede this “current” • Ohm’s Law: V=iR • Electrons are components of atoms. An Atom contains a nucleus of protons and other junk. The protons are the fundamental positive charges. Storage

7. Various Kinds of Electrical Materials • Conductors • Electrons move easily • Some are poor conductors – Resistors! • Insulators • Electrons are held tightly in place by their chemical bonds. • Semiconductors • Intermediate properties • Basis of transistors. Storage

8. Charge stuff • Potential Difference or Voltage • The work per unit charge required to move a charge from one point to the other • Current • The amount of charge that passes a single point in a circuit per unit time (1 sec). Storage

9. Plus … • Resistance • The ratio of the potential difference across a resistor (R=Ohms) to the current flowing THROUGH the resistor. • V=iR • This is Ohm’s Law Storage

10. A Magnet +Q S N Storage OP Survey

11. Magnets come in all shapes and sizes. Almost every refrigerator door has two to provide that last, snug pull when it closes. Storage

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14. Magnet Induces a Current in a Closed Circuit A Changing Magnetic Field Induces a Current Storage

15. Magnets • Magnets Do NOT attract chages. • Magnetism is a very different phenomenon. • Magnets have N and S poles • Like poles repel • Unlike poles attract • Where have we seem this before?? Storage

16. Other Observations • A magnet moving into a coil produces an electric current (and voltage!). • A wire moving near a magnet will have a current generated in it. • There is a “magnetic field” around a wire. • A loop of wire acts like a small magnet. Storage

17. What Reached the Ear? This is an ANALOG signal. The ear doesn’t respond to digital signals. Storage

18. The Process Processing Storage

19. Storage Methods • Analog Storage • Mechanical Electrical (Record, cylinder) • Magnetic (Tape, Wire) • Digital Storage • Magnetic (Tape) • Optical (CD) • Electrical (MP3 file on your “Flash Memory”) Storage

20. Issues • We want the process to be fast. • We want to be able to widely distribute the recorded product. • We want the product to reproduce, as well as possible, the original sound. • We want to ENJOY the final reproduction. Storage

21. OLDEN DAYS – (Screech of Chalk) Bell's ear Phonautograph was a very unusual variation on the basic technology. The recording mechanism was the human ear. By removing a chunk of skull including the inner ear from a human cadaver, and attaching a stylus to the moving parts of the ear, he was able to use this bio-mechanical device to make a recording of the sounds that entered a recording horn. It recorded on a moving glass strip, coated with a film of carbon, so there are probably no original recordings from it. Sound Human Ear Storage

22. Gramophone The graphophone in its original form was an improved form of the phonograph. One main difference, which Edison would soon adopt, was the use of a cardboard-coated wax cylinder instead of a sheet of tinfoil. The exact construction of the cylinders and the materials used changed considerably in later years, though the basic concept of recording into a soft, plastic material was retained. (image from NMAH) Storage

23. Development - Platter Storage

24. “HIS MASTERS VOICE” Woof! Woof! Storage

25. Western Electric Western Electric's recorder used electronic amplifiers to drive an electromagnetic cutting head, rather than relying on the acoustic horn. The result was a louder, clearer record. Storage

26. The Need for the Microphone Storage

27. An Old Carbon Microphone Storage

28. The Microphone • The microphone is a device that received the sound vibrations • converts it to an electrical “signal” • Which is then sent to the next stage in the process (later). • The signal tends to be small and gets weaker as it travels down a long wire. Storage

29. The Microphone Process MECHANCAL ---> --------------- ELECTRICAL Microphone Signal on a wire Storage

30. Consider a powder ofmetal Particles of Metal are pressed closer together. Resistance is reduced Storage

31. How does it work? Storage

32. The “Crystal” Microphone Storage

33. The Record Storage

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35. Dynamic Microphone Storage

36. Movies?? Image is Stretched Horizontally Storage

37. 1920 Wire Recorder Storage

38. 1930s Magnetic Tape Storage

39. Storage

40. Playback Storage

41. Yesterday and Today Symphony ~ 3-5 Disks @ 78 RPM ~50% of CD Storage

42. CD Storage

43. CD Storage

44. CD OPERATION Storage

45. Latest and Greatest 0.5 GB FLASH Storage

46. FLASH MEMORY Storage

47. Back to your head Storage

48. Storage

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50. Exploded View Storage