15'2 The Sound of Music

1
15.2 The Sound of Music
2

• Middle of 19th century
• German Hermann Helmholtz and English Lord
  Rayleigh
• studied how human voices produced sounds
• studied how instruments produced sounds
• studied how human ears detected sounds

3
Sources of Sound

• Vibrating objects
• vocal cords
• vibrate at air passes them
• brass instruments
• lips of performer vibrate
• reed instruments
• reed vibrates as air is blown across

4

• Open pipes
• air column vibrates
• stringed instruments
• string, sound board and air vibrates

5
Resonance

• What are the results of just the mouth piece of
  an instrument?
• Attach the rest of the instrument are what are
  the results?
• It is louder because of resonance

6

• The definition for resonance is to cause a
  vibration of a natural rate by a vibrating source
  having the same frequency
• piano string vibrates as someone nearby sings
• air column in organ vibrates

7
Closed-pipe resonator

• When one end of a pipe is closed
• organ
• slide whistle
• flute
• large seashell

8

• When a wave travels down the pipe and the back up
  the waves reinforce each other producing a
  standing wave

9
Open-pipe Resonator

• A tube with both ends open
• saxophone
• flute
• pipe organ
• overheads

10
The Quality of Sound

• The difference is sound from one instrument to
  another
• timbre sound quality depending upon both
  intensity and frequency

11

• Beat is a pulsing variation in loudness because
  of the superposition of two waves
• dissonance unpleasant sound
• consonance a pleasant sound
• fundamental the lowest note possible
• harmonics whole number multiplies of the
  fundamental