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WOODWIND INSTRUMENTS MUSICAL ACOUSTICS
The Science of Sound, Chapter 12 The Physics of Musical Instruments, Chapters 15 and 16
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WOODWIND INSTRUMENTS
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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
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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)
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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.
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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
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INPUT VALVES
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REED-GENERATOR CONFIGURATIONS
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
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TWO TYPES OF PRESSURE CONTROLLED VALVES
FLOW VELOCITY vs AIR PRESSURE IN A CLARINET
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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.
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CLARINET - RANGE OF PRESSURE
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CYLINDRICALPIPE RESONANCES (from Chap. 4)
CONICAL PIPE RESONANCES (see Fig. 12.7)
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WHAT ABOUT TRUNCATED CONES?
ARE THE RESONANCES HARMONIC?
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RESONANCE FREQUENCIES OF OPEN AND CLOSED PIPES, CYLINDRICAL AND CONICAL
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INPUT IMPEDANCE OF THE CLARINET
EFFECT OF REGISTER HOLES 3 REGISTERS OF A CLARINET
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EFFECTS OF REGISTER HOLES
p p p
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THREE NOTES ON A CLARINET
WAVEFORM SPECTRUM
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LATTICE OF OPEN TONE HOLES
CUTOFF FREQUENCY
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EFFECT OF REED STIFFNESS
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A CONICAL BORE ACTS LIKE A “CLOSED PIPE”
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CONTRABASS SAXOPHONE LARGEST WOODWIND INSTRUMENT
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OBOE WAVEFORM SPECTRUM
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BASSOON
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BASSOON
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EARLY WOODWIND INSTRUMENTS
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BAGPIPES HIGHLAND BAGPIPES
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NORTHUMBRIAN BAGPIPE
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DIRECTIONAL RADIATION
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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
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SPECTRAL ENVELOPE OF (IDEALIZED) WOODWIND
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FLOW CONTROL OF AIR BLOWN ACROSS A BOTTLE AND A FLUTE
CONSTRUCTION OF A FLUTE
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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)
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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
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FLUTE p OPENING TONE HOLES p REGISTER HOLES
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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
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BAROQUE RECORDER TYPICAL FINGERING CHART FOR A BAROQUE RECORDER
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BLOWING PRESSURE FLUTE, RECORDER
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Assignment for Wednesday:
Read Chapter 13 Exercises 1-6 p. 270
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