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sound vibration 1/3 octave

jc and Neil
 
I've gone back and captured some more side-by-side data. I've bumped up the acquisition rate for the TEAC to (next available step after 50kHz) 100kHz to get me a full 20kHz to analyze (the last band for the 1/3 octave is actually centered above 20kHz). I've also found and turned on the 40kHz filters to help with aliasing. I've attached an excel file with a few data sets. The data is not a problem as the differences don't show up until you're more than 60 dB down. I'm still a little concerned with the differences at the high frequencies but we can do some more 'real' tests.
 
We'll need to keep an eye on the noise floor of the TEAC. It is a 16-bit machine but the lowest I can set the input range is +-0.5V (15 micro volts).
 
The data shown is from a small desk fan. My accels have a very high frequency and I'm not exciting them at resonance.
 
Thanks for the feedback,
 
Frank
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It looks like increasing the sample rate and adding the anti-aliasing filter inverted the differences so that the TEAC data is now lower in amplitude at the high frequencies. The differences show up for low signal levels at the extremes of the measured band. Maybe my expectations are low, but, at this point, it may be difficult to get a better match on non-identical instruments.
jc
Mac 10.4
LV7.1
CLD
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jc,
 
Your expectations are in line with mine. I think we're doing pretty well. Besides two different instruments, the time series captured is not identical as the instruments are manually triggered. Life is good...
 
As I said though, we'll have to keep our eye on the noise floor and dynamic range of the TEAC. There are times we are measuring down to 30 dB.
 
Thanks again for responding.
 
Frank
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It is my pleasure to respond to these type questions. I have learned a lot from the discussion forums over the years. Problem solving forums like this are some of the most positive aspects of the internet. Good luck.
jc
Mac 10.4
LV7.1
CLD
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