Course:PHYS341/2018/Assignments/A8

Self-study for Quiz 8 on March 16th.

{The internal structure of a bowed instrument in the violin family is deliberately asymmetric because: |type="[]"} -(a) there are no frets on the fingerboard. || No. There are no frets because the notes can be sustained for long enough that small deviations from just intonation become a problem. Without frets, just intonation can be achieved. -(b) the bridge has a more complicated shape than that of a guitar. || No. The complication shape is to simulate voice formants above 2 kHz. -(c) the player sometimes needs to play more than one string at a time. || No. The curved top of the bridge allows this. -(d) of the stick-slip mechanism of the bowed strings. || No. That ensures that any fundamental frequency can be played. -(e) the bow produces a downward force on the bridge. || No. If it did, the soundbox would not need to asymmetric. See later discussion of the erhu - which is bowed more vertically and does have a symmetric soundbox. +(f) the bow produces a sideways force on the bridge. || Yes. A symmetric soundbox would simply be twisted rather than pumped.

{The stick-slip mechanism of the bow can excite a string at precisely the right frequency because: |type="[]"} +(a) the bow only grabs the string when it is moving at the same velocity as the string. || Yes, so the string gets a kick at precisely the right frequency. -(b) the bow only releases the string when it is moving at the same velocity as the string. || True. In fact it has to be true, but the release is no so important as the grab. -(c) the bow motion contains all frequencies. || Maybe one could argue this, but the situation is not analogous to a short pluck or strike containing all frequencies. -(d) the bow produces a sideways force on the bridge. || True but not relevant. -(e) the bow produces a downward force on the bridge. || True is the instrument is bowed liked an erhu, but this not relevant to the question. -(f) the tiny ridges on the horse hairs pluck the string. || No, they don't.

{A string on a lute-family instrument feels too slack, even when tuned to the right pitch. Which of the following solutions could work? |type="[]"} -(a) tighten the string. || No, that would change the pitch. +(b) replace the string with one of the same diameter but made of a heavier material. || Yes, then you would have to tighten the string to get the right pitch. -(c) replace the string with one of the same diameter but made of a lighter material. || No, that would be slacker. +(d) replace the string with one made of same material but thicker. || Yes, then you would have to tighten the string to get the right pitch.' -(e) replace the string with one made of same material but thinner. || No, that would be slacker.

{Why are higher strings on a piano tuned sharp and lower strings flat (the Railsback Curve)- compared to equal temperament? |type="[]"} -(a) We hear higher notes flatter than they are in reality || "No, we don't." -(b) We hear lower notes sharper than they are in reality || "No, we don't." +(c) Piano strings have noticeable inharmonicity, which increases the interval between partials. The piano is tuned to minimize beats between these partials. || "Yes." -(d) Piano keys play double and triple sets of strings. || "They do, but this extends the sustain and doesn't affect the tuning." -(e) It lowers the stress on the piano frame. || "This would be true for the heavy lower strings (opposite for the higher strings) but it is not the reason for the Railsback Curve."