ACOUSTICS OF WIND INSTRUMENTS

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ACOUSTICS OF WIND INSTRUMENTS
2. BRASS INSTRUMENTS
REFERENCES CHAPTER 11 IN SCIENCE OF SOUND
(ROSSING, et al.) CHAPTER 14 IN THE PHYSICS OF
MUSICAL INSTRUMENTS (F R) CHAPTERS 5 6 IN
MUSICAL INSTRUMENTS (CAMPBELL, et al.)
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FAMILIES OF BRASS INSTRUMENTS
VALVED BRASS INSTRUMENTS SLIDE BRASS
INSTRUMENTS NATURAL BRASS INSTRUMENTS KEYED OR
FINGERED BRASS INSTRUMENTS BRASS INSTRUMENTS MAY
BE CLASSIFIED ACCORDING TO MAIN BORE CYLINDRICAL
BORE (TRUMPET, TROMBONE, etc. CONICAL BORE
(CORNET, TENOR HORN, FRENCH HORN EUPONIUM, TUBA,
etc. SOME BRASS INSTRUMENTS COMBINE CYLINDRICAL
AND CONICAL
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SOME BRASS INSTRUMENTS
PLAYING RANGES
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COMPARISON OF BRASS INSTRUMENTS
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OSCILLATIONS IN A PIPE
THE AIR COLUMN OF A Bb TRUMPET HAS A LENGTH OF
ABOUT 140 cm. THE RESONANCES OF A CLOSED PIPE OF
THIS LENGTH SHOULD OCCUR AT fn nc/4L 343
n/4(1.4) 61.3 n (n 1 , 3, 5, 7, . . .)
61, 184, 306, 429 . . . Hz 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
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RESONANCES OF OPEN AND CLOSED PIPES
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RESONANCES OF CONICAL PIPES
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BRASS INSTRUMENTS WITH ESSENTIALLY CONICAL BORE
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CORNETT AND SERPENT
THE CORNETT (CORNETTO) IS ONE OF THE MOST
IMPORTANT INSTRUMENTS OF THE RENAISSANCE AND
BAROQUE PERIODS. IT HAS A SMALL BRASS-TYPE
MOUTHPIECE, A CONICAL BORE AND 7 FINGER HOLES
LIKE A RECORDER
THE SERPENT DEVELOPED IN LATE 16TH CENTURY
FRANCE. IT HAS 6 FINGER HOLES GROUPED IN TWO
SETS OF 3 EACH. ITS CURVED SHAPE ALLOWS THE
PLAYER TO REACH BOTH SETS. THE SPACING OF THE
TWO SETS OF FINGER HOLE MEANS THAT THE PLAYER
MUST PITCH THE NOTES LARGELY BY LIP POWER
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SERPENTS IN THE GARDEN
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KEYED BUGLE AND OPHICLEIDE
THE KEYED BUGLE DEVELOPED IN UK IN EARLY 19TH
CENTURY. IT HAS A CONICAL BORE AND 8 KEYS.
COMMONLY IN C WITH A CROOK TO LOWER IT TO Bb.
THE OPHICLEIDE, WHICH DEVELOPED IN FRANCE IN THE
19TH CENTURY, ALSO HAS A CONICAL BORE WITH LARGE
TONE HOLES AND AS MANY AS 12 KEYS. THE NAME
COMES FROM THE GREEK WORDS FOR SERPENT AND
KEYS
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DIDGERIDOO
THE DIDGERIDOO (DIDJERIDU) HAS BEEN PLAYED BY THE
ABORIGINES IN NORTHERN AUSTRALIA FOR AT LEAST
1500 YEARS. TRADITIONAL DIDGERIDOOS ARE FROM
EUCALYPTUS TREES HOLLOWED OUT BY TERMITES LENGTHS
VARY FROM 1 TO 3 m AND THE BORES VARY FROM
CYLINDRICAL TO CONICAL. IT HAS NO MOUTHPIECE AND
SO ITS IMPEDANCE IS LESS THAN THAT OF THE
PLAYERS VOCAL TRACT ALTHOUGH THE LOWEST PIPE
RESONANCE DETERMINES THE DRONE PITCH, A PROMINENT
VOCAL TRACT RESONANCE CAN BE VARIED BETWEEN 1.5
AND 2.5 kHz TO PROVIDE A STRONG AUDIBLE FORMANT
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BENADES WATER TRUMPET
(INPUT VALVE IS CONTROLLED BY PRESSURE FEEDBACK)
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MOUTHPIECE
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IMPEDANCE OF CYLINDER AND TRUMPET
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ADDING THE BELL
THE BELL CHANGES
THE FREQUENCIES AND HEIGHTS OF THE IMPEDANCE
PEAKS CHANGES THE RADIATION PATTERN (More
directional) CHANGES THE SPECTRUM OF THE RADIATED
SOUND ALLOWS MORE EFFICIENT SOUND RADIATION
(MATCHES IMPEDANCES)
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IMPEDANCES COMPARED TO A MUSICAL SCALE
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REFLECTION POINT IN THE BELL
THE TURNING POINT MOVES OUTWARD IN THE BELL AS
THE FREQUENCY INCREASES MODE FREQUENCIES ARE
NEARLY IN THE RATIOS 0.8 2 3 4
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TRUMPET SPECTRUM
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BERNOULLI EFFECT
REDUCED PRESSURE IN AIR JET FROM A VACUUM CLEANER
HOSE GIVES RISE TO A NET UPWARD FORCE FB
REDUCED PRESSURE IN THE CENTER SECTION CAUSES THE
LIQUID IN THE U-TUBE TO STAND AT A HIGHER LEVEL
BLOWING DOWNWARD THROUGH THE SPOOL CAUSES AIR TO
FLOW OUTWARD, SUPPORTING A CARD AND PIN BY MEANS
OF THE BERNOULLI FORCE
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SLIDES AND VALVES
PLAYING POSITIONS OF A TROMBONE SLIDE
PRESSING DOWN ON TRUMPET VALVE LENGTHENS THE THE
TRUMPET TUBING
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IMPEDANCE CURVES FOR TWO TROMBONES
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HAND IN A FRENCH HORN BELL
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PRESSURE INSIDE AND OUTSIDE A TRUMPET
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SHOCK WAVES IN BRASS INSTRUMENTS
ONLY A SMALL PART OF THE SOUND ENERGY THAT
REACHES THE BELL IS RADIATED THE REST IS
REFLECTED SOUND LEVELS AS HIGH AS 175 dB INSIDE A
TRUMPET NONLINEAR EFFECTS CREATE SHOCK WAVES
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TRANSIENTS
TRANSIENTS ARE IMPORTANT IN IDENTIFYING MUSICAL
INSTRUMENTS (see Section 7.11) BELOW CUTOFF
FEEDBACK STABILIZES OSCILLATION ABOVE CUTOFF
PARTIALS BUILD UP SLOWLY WITHOUT STRONG
FEEDBACK LIPS ARE MORE OR LESS ON THEIR OWN
UNTIL THE FIRST REFLECTED WAVE COMES BACK
TO ATTACK A NOTE CORRECTLY REQUIRES TRAINED
LIPS (ESPECIALLY ON A FRENCH HORN)
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MARCHING BAND INSTRUMENTS
BELL-FRONT VERSIONS OF BRASS INSTRUMENTS ARE
WIDELY USED BY MARCHING BANDS AND BY DRUM AND
BUGLE CORPS TRUMPETS AND FLUGELHORNS, ALTO
HORNS, MELLOHONES, FRENCH HORNS, TUBAS
ALTO HORN MARCHING FRENCH HORN
MARCHING TUBA
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MUTES
MUTES
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VIBRATIONS OF A TROMBONE BELL
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PERFORMANCE
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PRESSURE DISTRIBUTION
Winton Marsalis Trumpet
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(No Transcript)
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IMPEDANCE OF TROMBONE