Course:PHYS341/2019/pre-reading/Q4

For Quiz 4 on Feb. 2nd.

1 Circle statements that are correct. (Note - this one is not easy)

	(a) A pure sine wave has a simple spectrum with just one frequency.
	(b) Any repeated waveform has a spectrum consisting of partials whose frequencies are integer multiples of a fundamental frequency.
	(c) The less a repeated waveform looks like a simple sine wave, the richer the spectrum (i.e. many strong partials).
	(d) A repeated waveform that does not look like a sine wave has partials that are not integer multiples of a fundamental frequency.
	(e) A waveform of random but endlessly repeated shape has a random spectrum.
	(f) A waveform of random but endlessly repeated shape has a spectrum consisting of partials whose frequencies are integer multiples of a fundamental frequency.

2 A siren in the middle of an open field produces a pure tone at 3 kHz. You listen at the edge of the field. Now the tone changes frequency to 10 kHz with no change in acoustic power. What you hear is:

	(a) Quieter
	(b) Louder
	(c) Neither quieter nor louder

3 The tone changes back to the original 3 kHz, and then moves to 100 Hz, again with no change in acoustic power. What you hear is:

	(a) Quieter
	(b) Louder
	(c) Neither quieter nor louder

4 Two pure tones in the middle of piano range, a semitone apart (say concert A and A♯ i.e. 440 and 466 Hz) sound rough together because:

	(a) semitones sound bad together
	(b) the tones are beating together and so the excited area of the basilar membrane never settles down.
	(c) the waveform is no longer repetitive and so the excited area of the basilar membrane never settles down.
	(d) the tones excite areas of the basilar membrane that are too close together for the brain to figure out the central frequency.

5 Consult fig. 10-1 in your textbook. A 60 Hz tone of 90 dB will sound as loud as a 1000 Hz tone of how many dB?

	(a) 60 dB
	(b) 70 dB
	(c) 80 dB
	(d) 90 dB
	(e) 100 dB

6 Consult fig. 10-1 in your textbook. A 2000 Hz tone of 0 dB will sound as loud as a 10 dB tone at what frequency?

	(a) 50 Hz
	(b) 160 Hz
	(c) 320 Hz
	(d) 1200 Hz
	(e) 6700 Hz

7 A harp string has a fundamental frequency of 100 Hz (approx. G2, in musical notation). If it is plucked in the centre, what frequencies do you expect to show up in the sound spectrum?

	(a) 100 Hz only.
	(b) 200 Hz only.
	(c) 100, 200, 300, 400 Hz...
	(d) 100, 300, 500, 700 Hz...
	(e) 200, 400, 600 Hz.....
	(f) 200, 600, 1000 Hz.....

8 A guitar string has a fundamental frequency of 100 Hz (approx. G2, in musical notation). If it plucked one seventh of the way along the string with a thin plectrum, what frequencies do you expect to show up in the sound spectrum?

	(a) 700 Hz only.
	(b) 700, 1400, 2100 Hz ...
	(c) 700, 2100, 3500 Hz ...
	(d) 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 Hz ...
	(e) 100, 200, 300, 400, 500, 600, 800, 900, 1000 Hz ...
	(f) 100, 200, 300, 400, 500, 600, 700 Hz only

9 A qin string has a fundamental frequency of 100 Hz (approx. G2, in musical notation). If it plucked one seventh of the way along the string and touched lightly a third of the way along the string, what frequencies do you expect to show up in the sound spectrum?

	(a) 700 Hz only.
	(b) 700, 1400, 2100 Hz ...
	(c) 700, 2100, 3500 Hz ...
	(d) 300, 600, 900 Hz ...
	(e) 300, 400, 500, 600, 800, 900, 1000 Hz ...
	(f) 300, 400, 500, 600, 700, 800, 900, 1000 Hz ...

10 Playing the violin with the bow sul ponticello (i.e. close to the bridge) produces a brighter, harsher sound than playing sul tasto (i.e. bow over the fingerboard, further from the bridge) because:

	(a) Exciting any string closer to one end produces stronger high frequency harmonics.
	(b) The bow scrapes on the bridge.
	(c) You are bowing over the sound holes.
	(d) When playing sul tasto, the fingerboard absorbs sound.
	(e) Its all part of the magic of the violin.