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Physics 1251 The Science and Technology of Musical Sound

Physics 1251 The Science and Technology of Musical Sound. Unit 3 Session 29 MWF Brass Instruments . Physics 1251 Unit 3 Session 29 Brass Instruments.

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Physics 1251 The Science and Technology of Musical Sound

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  1. Physics 1251The Science and Technology of Musical Sound Unit 3 Session 29 MWF Brass Instruments

  2. Physics 1251 Unit 3 Session 29 Brass Instruments What pitch (frequency) does a clarinet play if the length from the reed to a hole is 19.5 cm (including end corrections, i.e. L′= 0.195 m) at 20 C? f = v/4L′ for a stopped cylinder; v =343 m/s f = 343/(4 ‧ 0.195) = 440 Hz.

  3. Physics 1251 Unit 3 Session 29 Brass Instruments 1′ Lecture: • Brass instruments are stopped pipes, that have a bore that is a combination of cylindrical and conical or flared. • Brass are excited by lip-valves. • The pitch is determined by feedback from the resonances of the pipe. • The pitch is changed by exciting various overtones and by changing the length of the pipe.

  4. Physics 1251 Unit 3 Session 29 Brass Instruments Brass Instruments of the Orchestra Euphonium Piccolo Trumpet Trumpet Trombone French Horn

  5. f1 f2 f3 f4 ♩ ♪ ♫ fn ~ ~ Physics 1251 Unit 3 Session 29 Brass Instruments Brass Instruments • The lips produce a pulsation in the pressure admitted to the pipe; the pressure standing wave feeds back to control the oscillations of the plays lips. Lip-valve pulsations Standing wave frequencies Feedback

  6. Physics 1251 Unit 3 Session 29 Brass Instruments The Origins of Brass: Shofar Sackbut Ocleidex Serpent

  7. Physics 1251 Unit 3 Session 29 Brass Instruments The Lip Valve 80/20Brass instruments are played by the player’s lips. Breath pressure, muscle tension and pressure feedback from the pipe determine the frequency of the opening and closing of the lips. Louis Armstrong – trumpet (1901-1971)

  8. Physics 1251 Unit 3 Session 29 Brass Instruments Embouchure Lip Valve

  9. Physics 1251 Unit 3 Session 29 Brass Instruments Lip Valve • The lips of the player act as a valve that admits pressure pulses into the pipe. • The frequency is determined by the breath air pressure, the lip tension and the resonances of the pipe.

  10. Physics 1251 Unit 3 Session 29 Brass Instruments 80/20Brass Instruments are stopped pipes. • The player’s lips produce a displacement node (pressure antinode) at the mouthpiece. • A displacement anti-node (pressure node) exists at the bell. Winton Marsalis Trumpet

  11. Physics 1251 Unit 3 Session 29 Brass Instruments Back Bore Cup The Mouthpiece

  12. Physics 1251 Unit 3 Session 29 Brass Instruments The Mouthpiece Cup Volume 80/20The Cup Volume and the diameter of the constriction leading to the back bore are more important than the shape of the cavity. Diameter

  13. Physics 1251 Unit 3 Session 29 Brass Instruments 80/20The Brass mouthpiece lowers the high frequency resonances. Resonance for Combination Pipes f Cone with mouthpiece Cone

  14. Physics 1251 Unit 3 Session 29 Brass Instruments The pitch is changed by pipe length and excitation of resonances. By means of slides and valves the length is changed.

  15. Physics 1251 Unit 3 Session 29 Brass Instruments

  16. Physics 1251 Unit 3 Session 29 Brass Instruments Horns can be played by exciting the resonances only. The “Natural Horns” No valves

  17. Pedal Tone Physics 1251 Unit 3 Session 29 Brass Instruments Resonance for Combination Pipes f Cone/ Cylinder % 0/100% 25/75% 40/60% 50/50% 20/80% 100/0%

  18. Physics 1251 Unit 3 Session 29 Brass Instruments Resonances for Combination Bores in Brass Instruments 80/20A 50% cylindrical ‒ 50% conical bore has a nearly harmonic series.

  19. Physics 1251 Unit 3 Session 29 Brass Instruments Cylindrical-Conical Instruments Cone French Horn Trombone Cylinder Cornet

  20. Cornet Flugel Horn Trumpet Physics 1251 Unit 3 Session 29 Brass Instruments Various instruments have different lengths of cylindrical and of conical pipe. Trumpet-like Instruments

  21. x Physics 1251 Unit 3 Session 29 Brass Instruments Exponential Horn The Bell a = ao exp(m x)+ b 80/20m is called the “flare constant.” Larger m means more rapid flare.

  22. a x Physics 1251 Unit 3 Session 29 Brass Instruments Bessel Horns The Bell a = ao e-(εx) +b 80/20Called “Bessel Horns” because the standing wave follows a Bessel Function.

  23. Physics 1251 Unit 3 Session 29 Brass Instruments Summary: • Brass Instruments are stopped pipes. • The pipe bore is designed to give resonances that are harmonic. • The pedal tone (the lowest note) is not harmonic. • The player’s lips are a soft reed. • The pitch is changed by changing the length and exciting resonances.

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