Physics 1251 The Science and Technology of Musical Sound - PowerPoint PPT Presentation

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Physics 1251 The Science and Technology of Musical Sound

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What pitch (frequency) does a clarinet play if the length from the ... Louis Armstrong trumpet (1901-1971) Physics 1251 Unit 3 Session 29. Brass Instruments ... – PowerPoint PPT presentation

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Title: Physics 1251 The Science and Technology of Musical Sound


1
Physics 1251The Science and Technology of
Musical Sound
  • Unit 3
  • Session 29 MWF
  • Brass Instruments

2
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • What pitch (frequency) does a clarinet play if
    the length from the reed to a hole is 19.5 cm
    (including end corrections, i.e. L' 0.195 m) at
    20 C?

f v/4L' for a stopped cylinder v 343
m/s f 343/(4 ? 0.195) 440 Hz.
3
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • 1' Lecture
  • Brass instruments are stopped pipes, that have a
    bore that is a combination of cylindrical and
    conical or flared.
  • Brass are excited by lip-valves.
  • The pitch is determined by feedback from the
    resonances of the pipe.
  • The pitch is changed by exciting various
    overtones and by changing the length of the pipe.

4
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Brass Instruments of the Orchestra

Euphonium
Piccolo Trumpet
Trumpet
Trombone
French Horn
5
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Brass Instruments
  • The lips produce a pulsation in the pressure
    admitted to the pipe the pressure standing wave
    feeds back to control the oscillations of the
    plays lips.

Lip-valve pulsations
Standing wave frequencies
Feedback
6
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • The Origins of Brass

Shofar
Sackbut
Serpent
Ocleidex
7
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • The Lip Valve
  • 80/20Brass instruments are played by the players
    lips.
  • Breath pressure, muscle tension and pressure
    feedback from the pipe determine the frequency of
    the opening and closing of the lips.

Louis Armstrong trumpet (1901-1971)
8
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Lip Valve

Embouchure
9
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Lip Valve
  • The lips of the player act as a valve that admits
    pressure pulses into the pipe.
  • The frequency is determined by the breath air
    pressure, the lip tension and the resonances of
    the pipe.

10
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • 80/20Brass Instruments
  • are stopped pipes.
  • The players lips produce a
    displacement node
    (pressure antinode)
    at the mouthpiece.
  • A displacement
    anti-node (pressure node)
    exists at the bell.

Winton Marsalis Trumpet
11
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • The Mouthpiece

Back Bore
Cup
12
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • The Mouthpiece

Cup Volume
80/20The Cup Volume and the diameter of the
constriction leading to the back bore are more
important than the shape of the cavity.
Diameter
13
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Resonance for Combination Pipes

80/20The Brass mouthpiece lowers the high
frequency resonances.
f
Cone with mouthpiece
Cone
14
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • The pitch is changed by pipe length and
    excitation of resonances.

By means of slides and valves the length is
changed.
15
Physics 1251 Unit 3 Session 29 Brass
Instruments
16
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Horns can be played by exciting the
    resonances only.

The Natural Horns No valves
17
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Resonance for Combination Pipes

f
Cone/ Cylinder
0/100
25/75
50/50
40/60
20/80
100/0
18
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Resonances for Combination Bores
    in Brass Instruments
  • 80/20A 50 cylindrical ? 50 conical bore has a
    nearly harmonic series.

19
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Cylindrical-Conical Instruments

Cone
French Horn
Trombone
Cylinder
Cornet
20
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Trumpet-like Instruments

Various instruments have different lengths of
cylindrical and of conical pipe.
21
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • The Bell

Exponential Horn
a ao exp(m x) b
80/20m is called the
flare constant. Larger m means more rapid flare.
22
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • The Bell

Bessel Horns
a ao e-(ex) b
80/20Called Bessel Horns because the standing
wave follows a Bessel Function.
23
Physics 1251 Unit 3 Session 29 Brass
Instruments
  • Summary
  • Brass Instruments are stopped pipes.
  • The pipe bore is designed to give resonances that
    are harmonic.
  • The pedal tone (the lowest note) is not harmonic.
  • The players lips are a soft reed.
  • The pitch is changed by changing the length and
    exciting resonances.
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