Physics of Sound: Music, Violins, Flutes, etc.. What is sound ? - Consists of pressure waves: compressions and rarefactions traveling from a source with.
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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 Singerf ~ 80 Hz – 300 Hz Soprano 300 Hz - 1100 Hz Human hearing Range: 30 Hz – 20,000 Hz
The violin is a wooden resonance box that amplifies the sound waves from the vibrations of the strings stretched across it. bridge How does the Violin Work ? 1.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
What’s up with the Strings ? Each string has a different mass and fundamental f o (pitch) G 3 (196 Hz) – most massive: vibrates more slowly, D 4 (293 Hz) A 4 (440 Hz) E 5 (660 Hz) – a thin, steel wire: vibrates most rapidly Frequency – controlled by length of string, tension, temperature.
Parts of a Violin 1.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 Fundamental harmonic (freq f = f o ) Second Harmonic (f = 2f o ) Third Harmonic (f = 3f o ) Length of String Anti-node (amplitude is max.) Node (amplitude = 0 ) Higher harmonics yield integer multiples of the fundamental f o f o Tension, 1/ density, (1/L)