Physics 2010
Belmont University
Teacher: Scott Hawley
1. A clarinet plays a soft note with an SIL of 40 dB. By what factor must the intensity be increased
in order to play the same note at an SIL of 70 dB
a. SIL2=SIL1 +10Log(I2/I1)
b. 70= 40 + 10Log(I2/I1)
c. 30= 10Log(I2/I1)
d. 103=(I2/I1) = 1000
2. A student engineer at the rock showcase said that the SIL at front-of-house was 117 dB. What
sound intensity does that correspond to? What pressure fluctuation does that correspond to?
a. SIL=SIL0 +10Log(I/I0)
b. 117=0+10Log(I/I0)
c. 1011.7= (I/I0) (example for logs: 1000 = 103 is the same as 3 = log101000.)
d. I=1011.7*10-12 = 10-.3
e. 0.5 W/m2
f. SPL=SPL0+20Log(∆P/∆P0)
g. 117=20Log(
3.
4. See Page 215 – 220
5. See page 222-225
6. 250,000ft3 according to the figure in the book, just under 2 seconds. 1.8 or 1.9s
7. Your home studio is 10ft X 7ft X 8ft. What are the frequencies of the five lowest-frequency room
modes?
a.
b. C/2*sqrt[(p/L)2+(q/w )2+(r/h)2 ] - (p,q,r is arranged randomly with values of 1, and 0.
Page 329 in Everest.)
c. 81.4, 71.3, 57.0, 91.2, 99.4
8. In Example “design” in Section 8.4 b&s
a. What material is used on the rear wall, and why?
i. Rear wall can be lined with an absorbent material to minimize reflection or
echo.
b. What is placed over the performers? Why?
i. A shell, to obtain fullness, a strong reflected sound, and intimacy
c. Briefly describe the construction of the hall’s side walls, and why this was chosen.
i. The side Walls are covered with absorbent material and splayed to eliminate
flutter echo.