the exciter mechanism of double-reed...
TRANSCRIPT
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
The exciter mechanism of double-reedinstruments
A. AlmeidaC.Vergez, R.Caussé
IRCAM – Centre Georges PompidouInstrument Acoustics and Analysis / Synthesis Teams
Sep 20, 2006 – Musical Acoustics Network Conference,London
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Motivations of my PhD work
General objectiveunderstand the behavior of double-reed instrumentscompare to other reed instruments
Applicationssound synthesisvalidate generic models of reedphysical interpretation for methods of fabrication ofdouble reeds
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
From reed to sound
Instrument
behavior
Sound
Reed
configuration
Material
properties
Fabrication
procedures
Embouchure
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
From reed to sound
Instrument
behavior
Sound
Reed
configuration
Material
properties
Fabrication
procedures
Embouchure
Empirical knowledge
(musician, reed maker)
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
From reed to sound
Instrument
behavior
Sound
Reed
configuration
Material
properties
Fabrication
procedures
Measurements
Physical
parameters
Embouchure
Empirical knowledge
(musician, reed maker)
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Outline
1 Reed instrument modelsResonatorExciter
2 Tools for reed characterisationReed characteristicsVibrational analysis
3 Conclusion
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Instrument models
Pressure varies periodically inside the bore (resonator):
Period of oscillations determined by the bore geometry
Pressure variations cause the reed to open and closeFlow and pressure are modulated by the reed opening,feeding the oscillation in the bore
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Instrument models
Pressure varies periodically inside the bore (resonator):
Period of oscillations determined by the bore geometry
Pressure variations cause the reed to open and closeFlow and pressure are modulated by the reed opening,feeding the oscillation in the bore
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Instrument models
Pressure varies periodically inside the bore (resonator):
Period of oscillations determined by the bore geometry
Pressure variations cause the reed to open and closeFlow and pressure are modulated by the reed opening,feeding the oscillation in the bore
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Instrument models
Pressure varies periodically inside the bore (resonator):
Period of oscillations determined by the bore geometry
Pressure variations cause the reed to open and closeFlow and pressure are modulated by the reed opening,feeding the oscillation in the bore
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Instrument models
Pressure varies periodically inside the bore (resonator):
Period of oscillations determined by the bore geometry
Pressure variations cause the reed to open and closeFlow and pressure are modulated by the reed opening,feeding the oscillation in the bore
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Outline
1 Reed instrument modelsResonatorExciter
2 Tools for reed characterisationReed characteristicsVibrational analysis
3 Conclusion
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Resonator
Measured oboe impedancefor note B3[Plitnik and Strong, 1979]
Linear systemPressure/flow independent of intensityDepends strongly on frequency
Reeds work on maxima of pressure/flow
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Outline
1 Reed instrument modelsResonatorExciter
2 Tools for reed characterisationReed characteristicsVibrational analysis
3 Conclusion
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Exciter modelMechanics
Linear spring model for the reed opening
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pr
pm
S
Displacement of the reed blades proportional to appliedforce [Almeida et al., 2006]Force caused by:
lipspressure difference pm − pr
S0 − S proportional to pm − pr
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Flow
Bernoulli model at the reed entrance
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pm
pr
(∆p)r
Flow induced by the pressure difference betweenmouth (pm) and reed (pr )Flow velocity (v ) proportional to (
√pm − pr )
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Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Non-linear characteristics
0 5 10 15 20
P P
Pressure
T M
(kPa)
0
0.05
0.1
0.15
0.2
0.25
Flow
(l/s)
RemarksDynamic effects neglectedPT = PM/3
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Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Comparison between instruments
−5 0 5 10 15 20 25 300
0.1
0.2
0.3
0.4
0.5Pressure flow characteristic
Pressure difference (kPa)
Flo
w (
l/s)
ClarinetOboeBassoon
Clarinet measurementat LAUM[Dalmont et al., 2003]
RemarkBassoon reed is wider than oboeClarinet opening still wider
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Comparison between instruments
0 1 2 3 4 5 60
0.2
0.4
0.6
0.8
1
1.2Normalized pressure flow characteristic
Pressure difference
Flo
w
ClarinetOboeBasoon
Clarinet measurementat LAUM[Dalmont et al., 2003]
ObservationDouble-reeds curve has longer tail beyond curve top(PT ∼ PM/5)Clarinet closer to theoretical model (PT ∼ PM/3)
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Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Outline
1 Reed instrument modelsResonatorExciter
2 Tools for reed characterisationReed characteristicsVibrational analysis
3 Conclusion
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Static characterisation
ObservationsNon-linear characteristic maintains shapeScale is determined by:
Reed elasticityReed opening at equilibrium
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Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Variability within a same reed
0 10 20 30 40 500
0.05
0.1
0.15
0.2
0.25
0.3
0.35
flow
(l/s
)
pressure (kPa)
natural cane reed no. 4 (humidified)
run 13run 14run 17
ReasonsReed damping changes along one experimentViscoelasticity (memory effects):
reed does not re-open instantly to the same positionmeasurements correspond to different reed openings atequilibrium
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Outline
1 Reed instrument modelsResonatorExciter
2 Tools for reed characterisationReed characteristicsVibrational analysis
3 Conclusion
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Dynamic properties of the reed
Reed does not behave equally when subject to a staticforce or to an oscillating onePrevious static characterisation needs to be completedwith an exploration of the dynamic properties of thereedDynamic effects are due to:
Inertia of the reed (cannot move between two statesinstantaneously)Inertia of the airViscosity and damping
In practice, the curve measured for static regimes ischanged when the frequency of oscillation changes
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Patterns of vibration in the reed
RemarksDifferent modes of vibration of the structure respond todifferent frequencies of the diving forceBoth the shape and frequency of these modes changewith the shape of the structure
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Patterns of vibration in the reed
RemarksDifferent modes of vibration of the structure respond todifferent frequencies of the diving forceBoth the shape and frequency of these modes changewith the shape of the structure
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Patterns of vibration in the reed
RemarksDifferent modes of vibration of the structure respond todifferent frequencies of the diving forceBoth the shape and frequency of these modes changewith the shape of the structure
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Patterns of vibration in the reed
RemarksDifferent modes of vibration of the structure respond todifferent frequencies of the diving forceBoth the shape and frequency of these modes changewith the shape of the structure
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Mechanical admittance of the reed
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000−50
0
50
100
Frequency (Hz)
Am
plitu
de (
dB)
Dry5 min soaking30 min soaking
RemarksDifferent modes of vibration of the structureRespond to different frequencies of the diving forceBoth the shape and frequency of these modes changewith the shape of the structure
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Observations
Sound ← Meas. ← GeometryInfluences:
sound amplitude
beating regime
closed/open time ratio
Char.changing S0 scales p,q
changing k scales p,q
admittance peaks⇒harmonic enhancementin final sound
induced flow dependson mode pattern
clarinet[Pinard et al., 2003]:important torsionalmode
Dyn.
Can be easilysimulated with FEMalgorithms
Simple models:clamped beam
Ex: increase tip mass⇒ increase 1st modefrequency
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Conclusion
RemarksBoth measurements shown are incomplete andcomplement each otherVibration modes and elastic properties are related tochanges in timbreComplex relation of measurements to final sound. . .. . . but a step towards understanding the role of thereed details
-
Double-reedphysics
Almeida
Motivations
ModelsResonator
Exciter
Tools for reedcharacterisa-tionReed characteristics
Vibrational analysis
Conclusion
Bibliography
Almeida, A., Vergez, C., and Caussé, R. (2006).Experimental investigation of reed instrument functionning through image analysis of reed opening.Submitted to Acustica.
Dalmont, J. P., Gilbert, J., and Ollivier, S. (2003).Nonlinear characteristics of single-reed instruments: quasi-static volume flow and reed openingmeasurements.J. Acoust. Soc. Am., 114(4):2253–2262.
Pinard, F., Laine, B., and Vach, H. (2003).Musical quality assessment of clarinet reeds using optical holography.J. Acoust. Soc. Am., 113(3):1736–1742.
Plitnik, G. and Strong, W. (1979).Numerical method for calculating input impedances of the oboe.J. Acoust. Soc. Am., 65(3):816–825.
MotivationsReed instrument modelsResonatorExciter
Tools for reed characterisationReed characteristicsVibrational analysis
Conclusion