2. 10-24-05 The Science of Music 1 Overview of Recording October 24, 2005

3. 10-24-05 The Science of Music 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.

4. 10-24-05The Science of Music3 ELECTROSTATIC RUBBINGS Think about this stuff - - - + - + - - dead cat

5. 10-24-05The Science of Music4 Forces Between Charges Q1Q1Q1Q1 Q2Q2Q2Q2AttractRepel ++X +-X -+X --X Q1Q1 Q2Q2 F

6. 10-24-05The Science of Music5 Coulomb’s Law – the math The Unit of Charge is the. The Unit of Charge is the Coulomb. The constant k=9 x 10 9 N-m 2 /C 2 The constant k=9 x 10 9 N-m 2 /C 2 or k=9,000,000,000 N-m 2 /C 2 or k=9,000,000,000 N-m 2 /C 2 d is measured in meters. d is measured in meters.

7. 10-24-05The Science of Music6 Electrical Charge The negative charge is identified with electrons. The negative charge is identified with electrons. Electrons can be “pushed around” wired (circuits) with the use of a battery. Electrons can be “pushed around” wired (circuits) with the use of a battery. “Resistors” impede this “current” “Resistors” impede this “current” Ohm’s Law: V=iR 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. Electrons are components of atoms. An Atom contains a nucleus of protons and other junk. The protons are the fundamental positive charges.

8. 10-24-05The Science of Music7 Various Kinds of Electrical Materials Conductors Conductors Electrons move easily Electrons move easily Some are poor conductors – Resistors! Some are poor conductors – Resistors! Insulators Insulators Electrons are held tightly in place by their chemical bonds. Electrons are held tightly in place by their chemical bonds. Semiconductors Semiconductors Intermediate properties Intermediate properties Basis of transistors. Basis of transistors.

9. 10-24-05The Science of Music8 Charge stuff Potential Difference or Voltage Potential Difference or Voltage The work per unit charge required to move a charge from one point to the other The work per unit charge required to move a charge from one point to the other Current Current The amount of charge that passes a single point in a circuit per unit time (1 sec). The amount of charge that passes a single point in a circuit per unit time (1 sec).

10. 10-24-05The Science of Music9 Plus … Resistance Resistance The ratio of the potential difference across a resistor (R=Ohms) to the current flowing THROUGH the resistor. The ratio of the potential difference across a resistor (R=Ohms) to the current flowing THROUGH the resistor. This is Ohm’s Law This is Ohm’s Law

11. 10-24-05The Science of Music10 A Magnet S N +Q OP Survey

12. 10-24-05 The Science of Music 11 Magnets come in all shapes and sizes. Almost every refrigerator door has two to provide that last, snug pull when it closes.

13. 10-24-05The Science of Music12

14. 10-24-05The Science of Music13

15. 10-24-05The Science of Music14 A Changing Magnetic Field Induces a Current Magnet Induces a Current in a Closed Circuit

16. 10-24-05The Science of Music15 Magnets Magnets Do NOT attract chages. Magnets Do NOT attract chages. Magnetism is a very different phenomenon. Magnetism is a very different phenomenon. Magnets have N and S poles Magnets have N and S poles Like poles repel Like poles repel Unlike poles attract Unlike poles attract Where have we seem this before?? Where have we seem this before??

17. 10-24-05The Science of Music16 Other Observations A magnet moving into a coil produces an electric current (and voltage!). 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. A wire moving near a magnet will have a current generated in it. There is a “magnetic field” around a wire. There is a “magnetic field” around a wire. A loop of wire acts like a small magnet. A loop of wire acts like a small magnet.

18. 10-24-05The Science of Music17 What Reached the Ear? This is an ANALOG signal. The ear doesn’t respond to digital signals.

19. 10-24-05The Science of Music18 The Process Analog Source Digital Storage Convert to Analog Speaker Analog Storage Retain Analog Speaker

20. 10-24-05The Science of Music19 Storage Methods Analog Storage Analog Storage Mechanical Electrical (Record, cylinder) Mechanical Electrical (Record, cylinder) Magnetic (Tape, Wire) Magnetic (Tape, Wire) Digital Storage Digital Storage Magnetic (Tape) Magnetic (Tape) Optical (CD) Optical (CD) Electrical (MP3 file on your “Flash Memory”) Electrical (MP3 file on your “Flash Memory”)

21. 10-24-05The Science of Music20 Issues We want the process to be fast. We want the process to be fast. We want to be able to widely distribute the recorded product. 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 the product to reproduce, as well as possible, the original sound. We want to ENJOY the final reproduction. We want to ENJOY the final reproduction.

22. 10-24-05The Science of Music21 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

23. 10-24-05The Science of Music22 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)

24. 10-24-05The Science of Music23 Development - Platter

25. 10-24-05The Science of Music24 “HIS MASTERS VOICE”

26. 10-24-05The Science of Music25 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.

27. 10-24-05The Science of Music26 The Need for the Microphone

28. 10-24-05The Science of Music27 An Old Carbon Microphone

29. 10-24-05The Science of Music28 The Microphone The microphone is a device that received the sound vibrations The microphone is a device that received the sound vibrations converts it to an electrical “signal” converts it to an electrical “signal” Which is then sent to the next stage in the process (later). 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. The signal tends to be small and gets weaker as it travels down a long wire.

30. 10-24-05The Science of Music29 The Microphone Process Microphone Signal on a wire MECHANCAL ---> ---------------  ELECTRICAL

31. 10-24-05The Science of Music30 Consider a powder of metal Particles of Metal are pressed closer together. Resistance is reduced

32. 10-24-05The Science of Music31 How does it work?

33. 10-24-05The Science of Music32 The “Crystal” Microphone

34. 10-24-05The Science of Music33 The Record

35. 10-24-05The Science of Music34

36. 10-24-05The Science of Music35 Dynamic Microphone

37. 10-24-05The Science of Music36 Back to the Future The Dynamic Microphone

38. 10-24-05The Science of Music37 Movies?? StretchedHorizontally

39. 10-24-05The Science of Music38 1920 Wire Recorder

40. 10-24-05The Science of Music39 1930s Magnetic Tape

41. 10-24-05The Science of Music40

42. 10-24-05The Science of Music41 Playback

43. 10-24-05The Science of Music42 Today

44. 10-24-05The Science of Music43 CD

45. 10-24-05The Science of Music44 CD

46. 10-24-05The Science of Music45 CD OPERATION

47. 10-24-05The Science of Music46 Latest and Greatest 0.5 GB FLASH

48. 10-24-05The Science of Music47 FLASH MEMORY

49. 10-24-05The Science of Music48 Back to your head

50. 10-24-05The Science of Music49

51. 10-24-05The Science of Music50

52. 10-24-05The Science of Music51 Exploded View

53. 10-24-05The Science of Music52 FULL CIRCLE!