PH 105

1
PH 105

• Dr. Cecilia Vogel
• Lecture 17

2
OUTLINE

• Resonances of string instruments
• Brass Instruments
• Lip reed
• Closed tube
• Effect of bell
• Registers
• timbre
• Playing scales

3
String Instrument Review

• Fundamental freq pitch
• determined by string.
• many harmonics produced by string, too.
• Spectrum timbre
• Resonances of bridge, plates, air cavity. enhance
  certain harmonics.

4
Timbre Demo

• A-string
• Expect strong
• 110 220 near resonances (fig 10.31)
• play C3 (131 Hz) 1st harm ___, 2nd ___
• G-string
• Expect strong fundamental and 2nd harm?
• 196 Hz and 392 Hz near resonances at 200 400 Hz
  (folk only)
• B-string
• f1 246.94 Hz, ___ and ___ harmonics
• near 250 Hz and 550 Hz resonance of classical

5
Brass Instruments

• An instrument is considered to be in the brass
  family if
• the source of disturbance for the sound is a
• i.e. the lips buzz in the mouthpiece to excite
  sound waves in the air inside
• Sound of a brass instrument is affected by sound
  source (_____), resonances (___________), and
  radiation (_____)

6
Feedback

• Can control pitch of lip reed
• by changing
• Hard to do with precision.
• Even harder to maintain.
• Once lips have started the air vibrating
• the pressure variations in the air
• This is called positive feedback.

7
Air Column Resonances

• The lip end of a brass instrument
• is a
• The cylindrical tube of a brass instrument WOULD
  resonate at freqs
• Where
• v speed of sound in air
• L length of tube
• n only odd integers
• BUT..

8
Bell Effect

• Adding a bell and mouthpiece
• makes the instrument longer,
• ________ all the resonant freqs.
• But the high freq resonances are affected more,
• so the resonances get

9
Bell Effect
1
3
5

• Resonances without bell
• and mouthpiece

ratio 5/3 1.67

• Resonances with bell
• and mouthpiece

ratio 3/2 1.5
10
Bell Effect

• Adding carefully tuned bell and mouthpiece
• makes resonances other than the lowest
• approximately ,
• even and odd,
• of a
• The lowest note of brass instrument,
• is not the fundamental frequency,
• but 2nd partial.
• Lowest resonance called pedal tone
• not often used, overtones not harmonic.

11
Open Notes of Brass

• B3b (233 Hz) uses 2nd resonance of tube

played note (fundamental of lip buzz)
harmonics of played note (harmonics in lip buzz)
12
Open Notes of Brass

• F4 uses 3rd tube resonance 349 Hz (which is a
  fifth above B3b)

played note
harmonics of played note
13
Open Notes of Brass

• B4b uses 4nd tube resonance at 466 Hz (which is
  an octave above B3b)

played note
harmonics of played note
14
Registers

• Can play B3b, F4, and B4b on trumpet
• by exciting different
• of the same
• These are the open notes of three different
  registers
• higher registers have weaker overtones
• Bugle can only play these notes.

15
Slides

• Trombone can play whole chromatic scale
• by changing the length of the tube.
• Slide a piece of tube out making it
• To go one semitone lower, the length of the tube
  should increase by
• 1/18 its current length.
• The lower you go, the
• fig 11.11

16
Seven Positions

• There are seven positions for trombone slide
• Position 7 gives you E2
• in the lowest
• Positions 6-1 let you go up 1-6 semitones.
• What if you wanted to go up 7 semitones?
• Thats a
• Can play that in 7th position
• Using slide in 2nd register,
• then in upper register.
• gets you all the way up to B3b

17
Valves

• Trumpet can play whole chromatic scale
• Pressing a valve brings an additional piece of
  tube into the airway
• making it
• One valve makes it one
• brings in extra 5.9 (about 1/18) of tube length.
• Another makes it two
• brings in extra 12.2 of tube length.
• Yet another makes it three
• brings in extra 18.9 of tube length.

18
Three Valves

• With only three valves, how do you go down more
  than 3 semitones?
• one three
• two three
• one two three
• 7 semitones is a
• can be played in
• Four semitones is more than
• logarithmic, not linear.
• Third valve tubing may have a slide, so it can be
  adjusted. Or you can adjust lip freq.

19
Brass Demo

• Listen to timbre. Observe spectrum.
• Play in different registers.
• What technique is used?
• What intervals can be played with same slide or
  valve position?
• (expect 2nd, 3rd 4th harmonics factors of 3/2
  or a perfect fifth and of 2 or an octave)
• Change of timbre with register
• Play chromatic scale using slide/valves.
• which slide positions are closer together? Why?

20
Summary

• Closed tube resonances,
• are changed by bell mouthpiece,
• brass instrument resonates at
• 2nd, 3rd, 4th, etc harmonics of missing fund.
• registers
• 3rd harmonic is up a fifth from 2nd
• 4th harmonic is up an octave from 2nd
• Trombone adds length with 7 positions of slide.
• Trumpet adds length with 3 valves.