The physics of brass musical instruments
This presentation is the property of its rightful owner.
Sponsored Links
1 / 20

The Physics of Brass Musical Instruments PowerPoint PPT Presentation


  • 57 Views
  • Uploaded on
  • Presentation posted in: General

The Physics of Brass Musical Instruments. Or, what do horn players do with their right hands, anyway? Brian Holmes SJSU Dept. Physics, [email protected] Intended structure of this talk. Standing waves Waves in tubes How to build a trumpet

Download Presentation

The Physics of Brass Musical Instruments

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


The physics of brass musical instruments

The Physics of Brass Musical Instruments

Or, what do horn players do

with their right hands, anyway?

Brian Holmes

SJSU Dept. Physics, [email protected]


Intended structure of this talk

Intended structure of this talk

  • Standing waves

  • Waves in tubes

  • How to build a trumpet

    • What horn players do with thei right hands (anyway).


Actual structure of this talk

Actual structure of this talk

  • One skit

  • A skit

  • Another digression (if time allows)

  • Much rushing to leave out material I nearly included


The physics of brass musical instruments

Playing frequencies of straight tube

Length: 1.41m

f

cyl

79

181

304

428

545

670


The physics of brass musical instruments

Playing frequencies of straight tube

Length: 1.41m

f/odd

f

cyl

79

181

304

428

545

670

79

60.3

60.8

61.1

60.6

60.9

v/4L = 60.4 Hz


The physics of brass musical instruments

What happens when you add the bell

f

f

bell

cyl

79

181

304

428

545

670

93

221

334

449

574

691


The physics of brass musical instruments

What happens when you add the bell

f

f

f

bell

cyl

79

181

304

428

545

670

93

221

334

449

571

691

14

40

30

21

26

21


The physics of brass musical instruments

What happens when you add the bell

f

f

% change

f

bell

cyl

79

181

304

428

545

670

93

221

334

449

571

691

14

40

30

21

26

21

--

22

9.9

4.9

4.8

3.1

The bell raises all the frequencies; but it raises

the low frequencies more than low frequencies.


The physics of brass musical instruments

  • Interpretation: the effective length of the    instrument is different from the actual    length.

  • High frequencies reflect closer to the open    end than low frequencies do.

  • The bell acts as a high-pass filter.

  • Above a cut-off frequency, no sound is    reflected back to the lips.

  • The cutoff-frequency is higher for a more    rapidly flaring bell.


Why make the bell an ineffective radiator of sound

Why make the bell an ineffective radiator of sound?

  • Because that makes the bell effective at reflecting sound back to the lips.

  • The sound returning to the lips gives feedback to them, controlling their vibrations and feeding more energy into the standing wave.

  • This control makes the instrument easier to play.


The physics of brass musical instruments

The mouthpiece has a

bowl-shaped cup that connects

to the conical backbore.

The backbore connects to

the conical leadpipe of the

instrument.


The physics of brass musical instruments

The column of the cup determines a popping frequency. Any sounds near this frequency will be amplified. The popping frequency of the trumpet mouthpiece is near 800 Hz.      A deeper cup will result in a lower popping frequency, yielding a less strident tone quality.


The physics of brass musical instruments

What happens when you add the

mouthpiece/leadpipe

f

f

f

cyl

bell

trumpet

79

181

304

428

545

670

93

221

334

449

571

691

93

232

348

465

578

696

Again the frequencies rise; and again, the

low frequencies rise more than the high ones.


The physics of brass musical instruments

What happens when you add the

mouthpiece/leadpipe

f

f

f

f /integer

cyl

bell

trumpet

tr

79

181

304

428

545

670

93

221

334

449

571

691

93

232

348

465

578

696

93

116

116

116

116

116

The playing frequencies are a set of multiples

of 116 Hz; except for the first multiple.


The physics of brass musical instruments

What if you put holes in the side of a trumpet?

The result, a keyed trumpet, would have uneven

tone quality.


The physics of brass musical instruments

Keyed bugles had a more even tone quality,

but didn’t sound like trumpets.


The physics of brass musical instruments

Other keyed instruments met with even less

success. For example, the Serpent.


The physics of brass musical instruments

And the Ophicleide.


The physics of brass musical instruments

Why do horn players keep

their hands in the bell, anyway?

  • To restore resonances above the cutoff    frequency.

  • To improve the tone quality of notes below    the cutoff frequency.

  • To adjust the intonation of the instrument.

  • To allow for special muting effects.

open

stopped


The physics of brass musical instruments

A good on-line reference

http://www.phys.unsw.edu.au/jw/brassacoustics.html


  • Login