music 150 musical acoustics
DESCRIPTION
MUSIC 150 MUSICAL ACOUSTICS. BRASS INSTRUMENTS. REFERENCE: CHAPTER 11 IN SCIENCE OF SOUND CHAPTER 14 IN THE PHYSICS OF MUSICAL INSTRUMENTS. SOME BRASS INSTRUMENTS. PLAYING RANGES. COMPARISON OF BRASS INSTRUMENTS. RESONANCES OF OPEN AND CLOSED PIPES. OSCILLATIONS IN A PIPE. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/1.jpg)
MUSIC 150 MUSICAL ACOUSTICS
BRASS INSTRUMENTS
REFERENCE: CHAPTER 11 IN SCIENCE OF SOUND CHAPTER 14 IN THE PHYSICS OF MUSICAL INSTRUMENTS
![Page 2: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/2.jpg)
SOME BRASS INSTRUMENTS
PLAYING RANGES
![Page 3: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/3.jpg)
COMPARISON OF BRASS INSTRUMENTS
![Page 4: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/4.jpg)
RESONANCES OF OPEN AND CLOSED PIPES
![Page 5: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/5.jpg)
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
![Page 6: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/6.jpg)
APPARATUS FOR GRAPHING THE ACOUSTIC IMPEDANCE OF WIND INSTRUMENTS
![Page 7: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/7.jpg)
FEEDBACK
![Page 8: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/8.jpg)
INPUT VALVES
![Page 9: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/9.jpg)
REED-GENERATOR CONFIGURATIONS
(a) Corresponds to a woodwind reed
(b) Corresponds to brass player’s lips
(c) Alternative model of brass player’s lips
![Page 10: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/10.jpg)
BENADE’S “WATER TRUMPET”(INPUT VALVE IS CONTROLLED BY PRESSURE FEEDBACK)
![Page 11: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/11.jpg)
MOUTHPIECE
![Page 12: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/12.jpg)
![Page 13: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/13.jpg)
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)
![Page 14: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/14.jpg)
IMPEDANCES COMPARED TO A MUSICAL SCALE
![Page 15: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/15.jpg)
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
![Page 16: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/16.jpg)
BERNOULLI EFFECT
REDUCED PRESSURE IN THE CENTER SECTION CAUSES THE LIQUID IN THE U-TUBE TO STAND AT A HIGHER LEVEL
REDUCED PRESSURE IN AIR JET FROM A VACUUM CLEANER HOSE GIVES RISE TO A NET UPWARD FORCE FB
BLOWING DOWNWARD THROUGH THE SPOOL CAUSES AIR TO FLOW OUTWARD, SUPPORTING A CARD AND PIN BY MEANS OF THE BERNOULLI FORCE
![Page 17: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/17.jpg)
SLIDES AND VALVES
PLAYING POSITIONS OF A TROMBONE SLIDE
PRESSING DOWN ON TRUMPET VALVE LENGTHENS THE THE TRUMPET TUBING
![Page 18: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/18.jpg)
IMPEDANCE CURVES FOR TWO TROMBONES
![Page 19: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/19.jpg)
HAND IN A FRENCH HORN BELL
![Page 20: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/20.jpg)
PRESSURE INSIDE AND OUTSIDE A TRUMPET
![Page 21: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/21.jpg)
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
![Page 22: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/22.jpg)
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)
![Page 23: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/23.jpg)
MUTES
MUTES
![Page 24: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/24.jpg)
VIBRATIONS OF A TROMBONE BELL
![Page 25: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/25.jpg)
PERFORMANCE
![Page 26: MUSIC 150 MUSICAL ACOUSTICS](https://reader036.vdocuments.us/reader036/viewer/2022062314/56812cfb550346895d91cc20/html5/thumbnails/26.jpg)
OBSERVING THE LIPS THROUGH A GLASS MOUTHPIECE WINDOW