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MUSIC
STANDING WAVES
At the right frequencies a constrained wave will produce a standing wave
Standing waves appear stationary Result of constructive and destructive
interference Have nodes and antinodes
NODES AND ANTINODES
Nodes Wave doesn’t move Destructive
interference Antinodes
Wave moves Constructive
interference
HARMONICS
Fundamental frequency Two nodes Half a wavelength in
between ends Pattern of standing
waves is called the harmonic series
HARMONIC SERIES
String or pipe open at both ends
n = 1, 2, 3, 4, … String – both ends
are nodes Open pipe – both
ends are antinodes
Pipe closed at one end
n = 1, 3, 5, … Pipe open at one
end – closed side in node, open side in antinode
INSTRUMENTS
Vibrating strings Violins, guitars, bass etc. Piano, harpsichord
Pipe open at both ends Flute
Pipe open at one end and closed at the other Saxophone, clarinet, trumpet, trombone, etc.
TIMBRE
Different instruments playing the same note sound different because of harmonics
The intensity of the harmonics varies between instruments
Changes the timbre, or sound quality of each instrument
BEATS When two waves of
different frequencies interfere the result is a complex interference pattern
The result is areas of constructive interference and areas of destructive interference
This amplitude variation are the beats
And the frequency with which they vary is the beat frequency
Beat frequency is the difference between the original two waves frequency
CONSONANCE AND DISSONANCE
Depends on the frequency difference between two tones
Varies between cultures and eras
Consonance Octave Perfect fourth Perfect fifth
Dissonance Minor second Major seventh