Wednesday, October 18, 2006
All About Sound, Parts 2, 3 and 4
Here are Part 2, Part 3, and Part 4 in the series about sound theory from the Audio DesignLine Website. These are also excerpted from Scott Janus' book "Audio in the 21st Century." There will be a test next Tuesday. ;^) I'd like to thank Scott Janus for allowing Henry Davis and the folks at Audio DesignLine for posting these articles. And of course thanks to Henry for his work as well.
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Correct me if I'm wrong, but if you look at the sample on page 2 of part 4, I think he made a mistake or typo.
ReplyDeleteassume (1) is air and (2) is water
Ө(2)= 1/sin * (sin Ө(2)*c(2)/c(1))
Ө(2) = 10°, so
sin(10°) = 0.1736, right?
c(2)/c(1) = 4921/1125 = 4.37 and
0.1736 * 4.37 = .7595
okay, so far, so good...
now 1/sin = 57.2986, so
57.2986 * .7595 = 43.52°, not 49.52°
They also calculated the wavelengths incorrectly because they used a frequency of 10 hertz instead of the 100 hertz, which was stated in the original problem. So instead of wavelengths of 112.5 ft and 492.1 ft, it should be 11.25 ft and 49.21 ft.
Or am I missing something here?