Physics 1251 The Science and Technology of Musical Sound

1
Physics 1251The Science and Technology of
Musical Sound

• Unit 4
• Session 37 MWF
• Synthesizers

2
Physics 1251 Unit 4 Session 37 Synthesizers

• In your own words, describe what a synthesizer is
  and what it does.

• A synthesizer
• is an electronic device
• is controlled by a player
• produces electro-acoustic signals
• simulates acoustic instruments
• generates novel and unique sounds.

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Physics 1251 Unit 4 Session 37 Synthesizers

• 1' Lecture
• A Synthesizer is a player-controlled electronic
  device creating electro-acoustical signals that
  emulate other instruments or generate unique
  sounds.
• Notes played by acoustic instruments pass through
  four phases (1) attack, (2) decay (3) sustain
  (4) release. (ADSR)
• Realistic synthesis requires sound to change with
  time in pitch, frequency recipe, and amplitude
  during the ADSR phases.
• Synthesizers are either analog or digital.
• Synthesizers employ either additive (or
  subtractive) synthesis or frequency modulation
  (FM).

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Physics 1251 Unit 4 Session 37 Synthesizers

• 80/20A Synthesizer is a player-controlled
  electronic device creating electro-acoustical
  signals that emulate other instruments or
  generate unique sounds.

What does that mean?
5
Physics 1251 Unit 4 Session 37 Synthesizers

• 80/20A Synthesizer is a player-controlled
  electronic device creating electro-acoustical
  signals that emulate other instruments or
  generate unique sounds.

Synthesizer
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Physics 1251 Unit 4 Session 37 Synthesizers

• 80/20A Synthesizer is a player-controlled
  electronic device creating electro-acoustical
  signals that emulate other instruments or
  generate unique sounds.

Synthesizer
Current I
Voltage V
I V/R
Ohms Law R V/I
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Physics 1251 Unit 4 Session 37 Synthesizers

• 80/20A Synthesizer is a player-controlled
  electronic device creating electro-acoustical
  signals that emulate other instruments or
  generate unique sounds.

Synthesizer
Current
Voltage
8
Physics 1251 Unit 4 Session 37 Synthesizers

• 80/20A Synthesizer is a player-controlled
  electronic device creating electro-acoustical
  signals that emulate other instruments or
  generate unique sounds.

Synthesis or the Real Thing?
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Physics 1251 Unit 4 Session 37 Synthesizers

• The first modern synthesizer was produced by RCA
  in 1955.
• The Moog (rhymes with vogue) synthesizer was
  invented in 1965 by Robert Moog.

First Moog Synthesizer
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Physics 1251 Unit 4 Session 37 Synthesizers

• ?Realistic synthesis requires emulation of
  realistic musical sounds.
• 80/20Musical sounds are characterized by four
  phases (1) attack (2) decay (3) sustain(4)
  release abbreviated ADSR.

Envelop
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Physics 1251 Unit 4 Session 37 Synthesizers

• 80/20Synthesizers use analog or digital
  processing.

80/20Synthesizers use analog or digital
processing.
Analog
Pressure
Sound Waves
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Physics 1251 Unit 4 Session 37 Synthesizers
80/20Synthesizers use analog or digital
processing.
Digital
Digital
Pressure
Sound Waves
80/20The amplitude of the waveform is digitized
and expressed as a binary number.
1000010000100001
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Physics 1251 Unit 4 Session 37 Synthesizers

• Digital to Analog Conversion (DAC)

1
2
DAC (Concept)
4
1010
8
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Physics 1251 Unit 4 Session 37 Synthesizers

• Electronic Digital-to-Analog Conversion

Input Number
Output Voltage
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Physics 1251 Unit 4 Session 37 Synthesizers

• Electronic Digital-to-Analog Conversion

Input Number
Output Voltage
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Physics 1251 Unit 4 Session 37 Synthesizers

• Electronic Digital-to-Analog Conversion

Input Number
Output Voltage
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Physics 1251 Unit 4 Session 37 Synthesizers

• Additive Synthesis
• The output signal is built up from a sum of
  harmonic signals.

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Physics 1251 Unit 4 Session 37 Synthesizers

• Frequency Modulation (FM) Synthesis
• In FM Synthesis the frequency fo of the signal is
  modulated up and down with a frequency fFM . The
  vibration recipe contains peaks at fo n fFM .

fo
fFM
Voltage Controlled Oscillator (VCO)
If fFM fo , then one produces a harmonic
series, f m fo .
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Physics 1251 Unit 4 Session 37 Synthesizers

• Summary
• A Synthesizer is a player-controlled electronic
  device creating electro-acoustical signals that
  emulate other instruments or generate unique
  sounds.
• Notes played by acoustic instruments pass through
  four phases (1) attack, (2) decay (3) sustain
  (4) release. (ADSR)
• Realistic synthesis requires sound to change with
  time in pitch, frequency recipe, and amplitude
  during the ADSR phases.
• Synthesizers are either analog or digital.
• Synthesizers employ either additive (or
  subtractive) synthesis or frequency modulation
  (FM).