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Physics of Sound: Music, Violins, Flutes, etc. What is sound ?. Consists of pressure waves: compressions and rarefactions traveling from a source with a speed dependent on the medium Clearly requires a medium If the pressure fluctuations are repetitive….
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Physics of Sound: Music, Violins, Flutes, etc.
What is sound ? • Consists of pressure waves: compressions and • rarefactions traveling from a source with a speed • dependent on the medium • Clearly requires a medium • If the pressure fluctuations are repetitive…. • you hear a tone with a pitch of characteristic frequency. • Bass Singer f ~ 80 Hz – 300 Hz • Soprano 300 Hz - 1100 Hz • Human hearing Range: 30 Hz – 20,000 Hz
How does the Violin Work ? bridge • Forward/Backward rubbing of bow makes strings vibrate • with different harmonic modes • 2. Energy is transferred from strings to belly via the bridge. • 3. Belly and the back of violin (via sound post) vibrate. • 4. Sound leaves violin thru F- holes The violin is a wooden resonance box that amplifies the sound waves from the vibrations of the strings stretched across it.
What’s up with the Strings ? Each string has a different mass and fundamental fo (pitch) G3 (196 Hz) – most massive: vibrates more slowly, D4 (293 Hz) A4 (440 Hz) E5 (660 Hz) – a thin, steel wire: vibrates most rapidly Frequency – controlled by length of string, tension, temperature.
Parts of a Violin • Strings – kept under tension. Sounds • produced by using bow or plucking • 2. Sound box – main body of violin • 3. Bow – drawn back and forth across • string. Relies on friction between rough • horsehair and string to make sounds F- holes communicate sound between interior and exterior
Harmonic Modes of a Vibrating String Tension and Length of a String sets the frequency of vibration fo Tension, 1/density, (1/L) Length of String Anti-node (amplitude is max.) Node (amplitude = 0 ) Fundamental harmonic (freq f = fo) Second Harmonic (f = 2fo ) Third Harmonic (f = 3fo) Higher harmonics yield integer multiples of the fundamental fo