Transcript WOODWIND INSTRUMENTS

MUSICAL ACOUSTICS
WOODWIND
INSTRUMENTS
The Science of Sound, Chapter 12
The Physics of Musical Instruments, Chapters 15 and 16
www.phys.unsw.edu.au/music/
WOODWIND INSTRUMENTS
OSCILLATIONS IN A PIPE
ONE WAY TO STUDY THE RESONANCES OF A PIPE
(OR A WIND INSTRUMENT) IS TO MAKE A GRAPH OF
ITS ACOUSTIC IMPEDANCE AS A FUNCTION OF
FREQUENCY
ACOUSTIC IMPEDANCE IS SOUND PRESSURE
DIVIDED BY VOLUME VELOCITY Z = p/U
APPARATUS FOR
GRAPHING THE
ACOUSTIC
IMPEDANCE OF
WIND
INSTRUMENTS
(from Chap. 11)
(The tube filled with
fiber-glass provides a
constant volume flow
from the driver, so
that the pressure
recorded by the
microphone is
proportional to
acoustic impedance)
HOW A CLARINET
WORKS
A pulse of excess
pressure propagates
down the pipe (a,b) and
is reflected as a pulse of
underpressure (c,d),
which returns to help
draw the reed valve shut.
In (e)-(h) the process
repeats with this
negative pulse, which
reflects as a positive
pressure pulse.
FEEDBACK
FEEDBACK—USE OF THE OUTPUT TO CONTROL OR
INFLUENCE THE INPUT
NEGATIVE FEEDBACK (IN HI-FIDELITY AMPLIFIERS)
STABLIZES A SYSTEM, REDUCES DISTORTION
POSITIVE FEEDBACK (IN OSCILLATORS OR MUSICAL
INSTRUMENTS) CAUSES INSTABILITY OR OSCILLATION
INPUT VALVES
REED-GENERATOR
CONFIGURATIONS
(a) INWARD STRIKING
Corresponds to a
woodwind reed
(b) OUTWARD STRIKING
Corresponds to brass
player’s lips
(c) SIDEWISE STRIKING
Alternative model of
brass player’s lips
TWO TYPES OF
PRESSURE
CONTROLLED
VALVES
FLOW VELOCITY vs
AIR PRESSURE IN A
CLARINET
HOW A CLARINET
WORKS
A pulse of excess
pressure propagates
down the pipe (a,b) and
is reflected as a pulse of
underpressure (c,d),
which returns to help
draw the reed valve shut.
In (e)-(h) the process
repeats with this
negative pulse, which
reflects as a positive
pressure pulse.
CLARINET - RANGE OF PRESSURE
CYLINDRICAL
PIPE
RESONANCES
(from Chap. 4)
CONICAL PIPE
RESONANCES
(see Fig. 12.7)
WHAT ABOUT TRUNCATED CONES?
ARE THE RESONANCES HARMONIC?
RESONANCE FREQUENCIES OF OPEN AND
CLOSED PIPES, CYLINDRICAL AND CONICAL
INPUT
IMPEDANCE OF
THE CLARINET
EFFECT OF
REGISTER
HOLES
3 REGISTERS OF A CLARINET
EFFECTS OF REGISTER HOLES
p
p
p
WAVEFORM
THREE NOTES
ON A
CLARINET
SPECTRUM
LATTICE OF
OPEN TONE
HOLES
CUTOFF
FREQUENCY
EFFECT OF REED STIFFNESS
A CONICAL BORE ACTS LIKE A “CLOSED PIPE”
CONTRABASS SAXOPHONE
LARGEST WOODWIND INSTRUMENT
WAVEFORM
OBOE
SPECTRUM
BASSOON
BASSOON
EARLY
WOODWIND
INSTRUMENTS
BAGPIPES
HIGHLAND
BAGPIPES
NORTHUMBRIAN
BAGPIPE
DIRECTIONAL RADIATION
TYPICAL BLOWING PRESSURES IN WOODWINDS
TYPICAL BLOWING PRESSURES ACROSS THE MAIN COMPASS OF CLARINET
ALTO SAXOPHONE, OBOE, AND BASSOON, FOR PIANO AND FORTE PLAYING
Fuks and Sundberg, 1996
SPECTRAL ENVELOPE OF (IDEALIZED) WOODWIND
FLOW CONTROL
OF AIR BLOWN
ACROSS A
BOTTLE AND A
FLUTE
CONSTRUCTION
OF A FLUTE
PRESSURE STANDING WAVES IN A FLUTE
IF THE CORK IS PULLED OUT, ALL NOTES ARE FLATTENED BUT UPPER
MODES ARE AFFECTED MORE (BECAUSE THE EFFECTIVE POSITION OF THE
PRESSURE MODE AT THE BLOWING END IS BEYOND THE CORK)
BLOWING PRESSURE USED
BY EXPERIENCED FLUTE
PLAYER FOR NOTES OF
DIFFERENT PITCHES
LIP OPENING WIDTH AND HEIGHT
USED BY EXPERIENCED FLUTE
PLAYERS TO PRODUCE NOTES
AT DIFFERENT PITCHES AND
VOLUME LEVELS
FLUTE
p
OPENING TONE
HOLES
p
REGISTER
HOLES
TYPICAL SPECTRA FOR LOUD AND SOFT NOTES OF VARIOUS PITCHES PLAYED
BY 4 DIFFERENT FLUTISTS. THE SAME REFERENCE LEVEL IS USED IN EACH
CASE
Fletcher, 1975
BAROQUE
RECORDER
TYPICAL
FINGERING
CHART FOR A
BAROQUE
RECORDER
BLOWING PRESSURE
FLUTE, RECORDER
Assignment for Wednesday:
Read Chapter 13
Exercises 1-6 p. 270