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271828 (Structural)
3 Jun 10 21:39
Hello all. I do a fair amount of work with structural vibrations, but our usual frequency band of interest is fairly narrow, like 0-20 Hz. No background in acoustics or higher frequency mechanical vibrations. Therefore, I've never had to deal with plots using one-third-octaves. I've done some reading online and have an idea of what's going on, but not quite enough to allow me to really deal with these effectively. My current application is checking a structure's ability to support a CT scanner. The manufacturer's tolerance plot is a spectrum with log scale rms acceleration vs One-Third-Octave Center Frequency in Hz. I'm not sure how to turn this into a spectrum with linear x and y axes for comparison with the predicted acceleration spectrum. If someone would be kind enough to point me to a good discussion, I'd appreciate it. 字串1
BTW, I searched, but only found the following, which was helpful, but I need more.
http://www.eng-tips.com/viewthread.cfm?qid=150400
GregLocock (Automotive)
4 Jun 10 0:35
The y axis is the rms of the enrgy in each third octave band, each of which has a bandwidth 22% of its centre frequency.
So the psd is a horizontal line, height (rms_accel_in band)^2/(.22*centre frequency of band in hz).
However you'd be better off turning your linear Hz measurement into third octaves for comparison.
Cheers
Greg Locock
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