Course:PHYS341/2019/pre-reading/Q7

Self-study for Quiz 7 on March 11th.

1 Why does a string, stretched along a rigid bar, make very little sound when plucked? The string is completely free to vibrate.

	(a) The bar is too heavy.
	(b) The bar is too light.
	(c) The string is too thick.
	(d) The string is too thin.

2 You listen to two recordings of sound of a single note with an accurate pitch of middle C, with no vibrato. One is produced by a trained human voice, one by a long even bow stroke on a cello string. You have no trouble telling which is which. Why?

	(a) the frequencies are different
	(b) the cello sound has a harmonic spectrum
	(c) the voice sound has a harmonic spectrum
	(d) Both sounds are harmonic but the shapes of the spectra are different
	(e) The cello has a missing fundamental.
	(f) the voice has a missing fundamental.

3 The modern piano (starting c. 1870) with its steel frame was a technological advance on the wooden framed fortepianos for which of the following reasons (more than one)?

	(a) Steel is more dimensionally stable than wood, and so the strings can be set at a higher tension.
	(b) Steel is more dimensionally stable than wood, and so the piano stays in tune longer.
	(c) Steel is stronger than wood, allowing the strings to be thicker, with better bass, and less inharmonicity.
	(d) Steel is stronger than wood, allowing the strings to be set to a higher tension, with more sound and less inharmonicity.
	(e) Steel is stronger than wood, allowing a larger soundboard with a better bass sound.
	(f) Steel is heavier than wood and a heavier frame gives a better bass sound.

4 String instruments often have a hole (or holes) because (three good reasons):

	(a) The sound echoes in the hole.
	(b) The hole lets the sound out of the box.
	(c) The air in the neck of the hole radiates sound well at low frequencies.
	(d) The hole adds an extra low resonance to the sound box related to the Helmholtz "beer bottle" resonance.
	(e) The hole lowers the lowest frequency of the sound box without having to thin the sound board too much.
	(f) The hole allows you to look inside to see how well the instrument is made.