The Science of Sound, Chapter 12
The Physics of Musical Instruments, Chapters 15 and 16 www.phys.unsw.edu.au/music/

WOODWIND INSTRUMENTS

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 —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

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

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

OPENING TONE
HOLES
REGISTER
HOLES p p

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