Course:PHYS341/2018/Calendar/Lecture 25
Phys341 Lecture 25: Summary and web references
2018.03.12
Textbook Ch.16.2, 17.5-17.10
- String materials
- Harps https://www.youtube.com/watch?v=cTV5vpe7GIk
- Harpsichords https://www.youtube.com/watch?v=ryQ2WjmcYWI
- The Piano https://www.youtube.com/watch?v=S6wNh45VpLc
- Striking a string https://www.youtube.com/watch?v=tfiV7V7eH1Q
- Sympathetic strings
- 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.
- 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).