physics 1251 the science and technology of musical sound

Physics 1251Physics 1251The Science and The Science and

Technology of Musical Technology of Musical SoundSound

Physics 1251Physics 1251The Science and The Science and

Technology of Musical Technology of Musical SoundSound

Unit 4Unit 4

Session 38 MWFSession 38 MWF

Analog Recording and Analog Recording and PlaybackPlayback

Unit 4Unit 4

Session 38 MWFSession 38 MWF

Analog Recording and Analog Recording and PlaybackPlayback

Physics 1251Physics 1251 Unit 4 Session 38Unit 4 Session 38 Analog RecordingAnalog Recording

Who is Robert Moog and why is he Who is Robert Moog and why is he important?important?

Robert Moog (rhymes with Robert Moog (rhymes with vogue) vogue)

invented the Moog Synthesizer, invented the Moog Synthesizer, a a

pioneering instrument in the pioneering instrument in the development development

of the synthesizer.of the synthesizer.


11′ Lecture:′ Lecture:

• Recording requires a transducer, such as a Recording requires a transducer, such as a microphone, to produce an electrical signal. microphone, to produce an electrical signal.

• Common types of microphones are (1) Common types of microphones are (1) condenser; condenser; (2) magnetic; (3) dynamic; (4) ribbon; (5) (2) magnetic; (3) dynamic; (4) ribbon; (5) piezoelectric; (6) carbon.piezoelectric; (6) carbon.

• Recording also requires amplification as well as a Recording also requires amplification as well as a storage medium.storage medium.

• Analog recording media include vinyl record, Analog recording media include vinyl record, magnetic tape, magnetic disk and optical film.magnetic tape, magnetic disk and optical film.

• Playback uses physical principles in which Playback uses physical principles in which mechanical oscillations, magnetic domains and mechanical oscillations, magnetic domains and optical density variations produce electrical optical density variations produce electrical signals that are analogous to the recorded sound.signals that are analogous to the recorded sound.


80/2080/20An electric guitar uses a magnetic An electric guitar uses a magnetic pickup that produces an electrical pickup that produces an electrical signal by a time-varying magnetic signal by a time-varying magnetic field.field.

Steel Guitar Steel Guitar StringString

PickupPickup

NN

SS


80/2080/20The Faraday Effect : a magnetic field The Faraday Effect : a magnetic field that varies in time produces a that varies in time produces a voltage and current in a coil.voltage and current in a coil.

N N SS

CurreCurrentnt


80/2080/20A Condenser Microphone uses A Condenser Microphone uses electric induction to produce an electric induction to produce an electrical signal.electrical signal.

Voltage VVoltage V

Current ICurrent I

++

++

++

++

Charge = V (Charge = V (εεoo S/x)S/x)

++

++

++

++

++

++

++

++


80/2080/20Magnetic Microphone: a small Magnetic Microphone: a small magnet, attached to a moving magnet, attached to a moving diaphragm induces a voltage and diaphragm induces a voltage and current in a coil.current in a coil.

Voltage VVoltage V

Current ICurrent I


80/2080/20Dynamic Microphone: a diaphragm Dynamic Microphone: a diaphragm moves a small coil in a magnetic moves a small coil in a magnetic field inducing a voltage and current.field inducing a voltage and current.

Voltage VVoltage V

Current ICurrent I

NN

NN

SS


80/2080/20A Ribbon Microphone uses a light A Ribbon Microphone uses a light weight ribbon of metal moving in a weight ribbon of metal moving in a magnetic field to produce electrical magnetic field to produce electrical signals.signals.

Current ICurrent I

Voltage VVoltage VNN SS


80/2080/20Piezoelectric Microphone: a thin Piezoelectric Microphone: a thin crystal is bent which produces a crystal is bent which produces a small voltage.small voltage.

Voltage VVoltage V++

++

--

++

++

++

--

++

++

++

--

++


80/2080/20Carbon Microphone: a diaphragm Carbon Microphone: a diaphragm compresses a sealed container of compresses a sealed container of carbon granules, changing its carbon granules, changing its resistance.resistance.

Voltage VVoltage V

Current ICurrent I

I = V/RI = V/R


Microphones:Microphones:

• Electrostatic—InductionElectrostatic—Induction• Condenser Condenser

• Magnetic—Faraday EffectMagnetic—Faraday Effect• MagneticMagnetic• DynamicDynamic• RibbonRibbon

• Piezoelectric—Piezoelectric EffectPiezoelectric—Piezoelectric Effect• Carbon—Ohm’s LawCarbon—Ohm’s Law


80/2080/20A Vacuum Tube is an electronic A Vacuum Tube is an electronic device that amplifies electrical device that amplifies electrical signals by permitting a small voltage signals by permitting a small voltage to modulate a much larger current.to modulate a much larger current.

VVoutout

CathodeCathode

PlatePlate

GridGrid

VVinin

Gain = Gain = VVoutout /V /Vinin


Amplification:Amplification:

Gain G = VGain G = Voutout / V / Vinin

VVoutout

VVinin

VVoutout = G V = G Vinin


80/2080/20A Field Effect Transistor (FET) is a A Field Effect Transistor (FET) is a solid state electronic device that solid state electronic device that permits amplification of electrical permits amplification of electrical signals.signals.

SourceSourceGateGate

DrainDrain

SiliconSiliconSilicon Silicon DioxideDioxide


Analog Recording Media:Analog Recording Media:

• MechanicalMechanical• Edison’s PhonographEdison’s Phonograph• Vinyl LP RecordsVinyl LP Records

• MagneticMagnetic• Magnetic TapeMagnetic Tape• Magnetic DiskMagnetic Disk

• OpticalOptical• Audio Track on motion picture filmAudio Track on motion picture film


Mechanical:Mechanical:

• Edison’s PhonographEdison’s Phonograph


Mechanical:Mechanical:

• Edison’s PhonographEdison’s Phonograph• Vinyl LP RecordsVinyl LP Records

Analog Recording Media:Analog Recording Media:• MagneticMagnetic

• Magnetic TapeMagnetic Tape• Magnetic DiskMagnetic Disk



Analog Recording Media:Analog Recording Media:• MagneticMagnetic

• Magnetic TapeMagnetic Tape• Magnetic DiskMagnetic Disk

Ferro-Ferro-metal metal OxideOxide

TracksTracks


Analog Recording Media:Analog Recording Media:• OpticalOptical

• Audio Track on motion picture filmAudio Track on motion picture film

Stereo Audio Stereo Audio TracksTracks


Summary:Summary:• Common types of microphones are (1) Common types of microphones are (1)

condenser; condenser; (2) magnetic; (3) dynamic; (4) ribbon; (2) magnetic; (3) dynamic; (4) ribbon; (5) piezoelectric; (6) carbon.(5) piezoelectric; (6) carbon.

• Vacuum tubes and transistors provide Vacuum tubes and transistors provide amplification by permitting the input to amplification by permitting the input to modulate a larger output current and voltage.modulate a larger output current and voltage.

• Analog recording media include mechanical, Analog recording media include mechanical, magnetic and optical storage.magnetic and optical storage.

• Playback uses physical principles in which Playback uses physical principles in which mechanical oscillations, magnetic domains mechanical oscillations, magnetic domains and optical density variations produce and optical density variations produce electrical signals that are analogous to the electrical signals that are analogous to the recorded sound.recorded sound.

physics 1251 the science and technology of musical sound

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