Answers
to the in-class exercises:
1. (2x10 –3 dynes/cm2)
20
log ----------------------- =
20 log 10 = 20 (1) = 20 dB SPL
(2x10 –4 dynes/cm2)
2. (10 –12 W/cm2)
10
log ----------------------- =
10 log 104 = 10 (4) =
40 dB IL
(10 –16 W/cm2)
3. (10 –8 W/m2)
10
log ----------------------- =
10 log 104 = 10 (4) =
40 dB IL
(10 –12 W/m2)
4. (2x10 –4 N/m2)
20
log ----------------------- =
20 log 10 = 20 (1) = 20 dB SPL
(2x10 –5 N/m2)
You
should be able to set the rest up from the above examples. Here are the
answers. Email me if there are any questions.
5. 40 dB SPL
6. 80 dB SPL
7. 14 dB SPL
8. 34 dB SPL
9. 74 dB SPL
10. 0 dB SPL
11. 40 dB SPL
1. X
20
log ----------------------- =
140 dB SPL
(2x10 –5 N/m2)
X
log ----------------------- = 7
(2x10 –5 N/m2)
X
----------------------- =
107
(2x10 –5 N/m2)
X = (107)(2x10 –5 N/m2)
X = 200 N/m2 or
2x102 N/m2
You
should be able to set up the rest using the above example (remember to use the
intensity 10 log formula if you use the intensity reference values). Yes, a
couple of these end up with 10 raised to a weird number like 3.7 or 3.3. You
should still be able to work them but I will not give you weird ones like that
on the test.
2. 2x10 –5 N/m2
3. 2x10 –1 N/m2
4. 2x10 –4 N/m2
5. 0.1 N/m2 or
10 –1 N/m2
6. 0.04 N/m2 or
4x10 –2 N/m2
7. 10 –12
W/m2
8. 10 –2
W/m2