Course:PHYS341/Archive/2016wTerm2/Assignments/A8

Practice Questions for Quiz 8, Friday Mar 24

Textbook sections covered: (18.1-6,18.10), (19.1-4,19.7)

1. If a woodwind instrument is played with only the first three 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 fourth hole, precisely.
(e) a little way upstream of the fourth hole.
(f) a little way downstream of the fourth hole.✓

2. On a woodwind instrument, if the register hole is opened when all other holes are covered -

(a) an extra pressure node appears in the standing wave inside the bore and the instrument plays in a higher register.✓
(b) an extra velocity node appears in the standing wave inside the bore and the instrument plays in a higher register.
(c) an extra pressure node appears in the standing wave inside the bore and the instrument plays in a lower register.
(d) an extra velocity node appears in the standing wave inside the bore and the instrument plays in a lower register.

3. 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.

4. 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. ✓

and thus

(i) suppresses lower frequencies.
(ii) suppresses higher frequencies. ✓