Course:PHYS341/2018/Calendar/Lecture 25

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Phys341 Lecture 25: Summary and web references

2018.03.12

Textbook Ch.16.2, 17.5-17.10

  1. String materials
  2. Harps https://www.youtube.com/watch?v=cTV5vpe7GIk
  3. Harpsichords https://www.youtube.com/watch?v=ryQ2WjmcYWI
  4. The Piano https://www.youtube.com/watch?v=S6wNh45VpLc
  5. Striking a string https://www.youtube.com/watch?v=tfiV7V7eH1Q
  6. Sympathetic strings
  7. Two decay curves.
    • Ear locks onto the loud fast decay mode.
    • Can continue to hear the soft slow decay that follows.
    • “Soft” pedal – una corda
    • Hammer strike only one string
    • Other string(s) pick up vibrational energy from struck string.
  8. Piano Tuning
    • Thick wire strings are not perfectly harmonic
    • Partials are stretched slightly and progressively sharp.
    • Multi-stringed instruments with thick strings need “stretch tuning” to avoid beating between inharmonic partials.
    • Low notes tuned somewhat flat; high notes tuned somewhat sharp.
    • The plot of frequency against key number is called the “Railsback Curve”.
    • This is one reason why piano tuning is a career option, rather than a casual activity. (The other reason is beating between sympathetic strings).
    • Harp tuning has similar issue (but without the complication of sympathetic strings).