Course:PHYS341/2018/Assignments/A9

Self-study for Quiz 9 on March 28th.

1 If a woodwind instrument is played with only the first two holes and register hole covered, the pressure node of the standing wave inside will be -

	(a) at the third hole, precisely.
	(b) a little way upstream of the third hole.
	(c) a little way downstream of the third hole.
	(d) at the second hole, precisely.
	(e) a little way upstream of the second hole.
	(f) a little way downstream of the second hole.

2 A double-reed woodwind instrument has a standing wave spectrum of frequency ratios -

	(a) approximately 1:2:3:4... if the bore is cylindrical.
	(b) approximately 1:2:3:4... if the bore is conical.
	(c) approximately 1:3:5:7... if the bore is cylindrical.
	(d) approximately 1:3:5:7... if the bore is conical.

3 The bell of a brass instrument behaves as

	(a) a closed pipe for lower frequencies.
	(b) a closed pipe for higher frequencies.
	(c) an open pipe for lower frequencies.
	(d) an open pipe for higher frequencies.
	(e) an infinitely long pipe for lower frequencies.
	(f) an infinitely long pipe for higher frequencies.

4 and thus:

	(i) suppresses standing waves in the pipe of higher frequencies.
	(ii) suppresses standing waves in the pipe of lower frequencies.

5 A xylophone will sound brighter than a marimba, even if the two instruments are made of the same wood and the bars are of similar size, because -

	(a) The xylophone bars are tuned with the first two bending modes in ratio 1:3 which coincide with the first two modes of the resonating tube.
	(b) The xylophone bars are tuned with the first two bending modes in ratio 1:4 which coincide with the first two modes of the resonating tube.
	(c) The marimba bars are tuned with the first two bending modes in ratio 1:3 which coincide with the first two modes of the resonating tube.
	(d) The marimba bars are tuned with the first two bending modes in ratio 1:4 which coincide with the first two modes of the resonating tube.

6 A bass drummer aims to excite the (0,1) mode of the drum membrane. A timpanist aims to excite the (1,1) mode of the drum membrane. Where on the drum should each player strike the instrument? (See http://hyperphysics.phy-astr.gsu.edu/hbase/Music/cirmem.html).

	(a) Edge (bass drum), centre (timpani)
	(b) Edge (bass drum), edge (timpani)
	(c) Centre (bass drum), edge (timpani)
	(d) Centre (bass drum), between the centre and the edge (timpani)
	(e) Between the centre and the edge (bass drum), centre (timpani)
	(f) Between the centre and the edge (bass drum), between the centre and the edge (timpani)