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Forgot to say, there is vibration noise of course of the plates that support mic and fan structure and other noises that i suppose come from the fan beeing old and the lubrication is not the best. The former is is pretty audible but the latter is very low.

Once again thank you for all your feedback I'm very grateful. I'm measuring the sound in a lab with some background noise. The mic is in downstream approx. 20 cm from the fan, but as long as I get closer I can use a windscreen, so no problems in noise there. I've used the suggestion to measure...

Hello again! TMoose, sorry for asking again. What I have been seeing about synchronizing data was calculating cross correlation between signals so it is possible to "align" them in the time axis, using maximum correlation. Beeing this non-stationary and noisy I don't see how it's possible to do...

Hello and sorry for taking so much time to reply. First thank you all for your feedback! GregLocock: 1st: I can't hear the difference 2nd: I have SP toolbox yes and I already tried to search for that time structure at 1/rev sec, using empirical mode decomposition and hilbert spectrum but i...

Hello ! I don't know if this is the right forum but here it goes: I'm doing a thesis on defect identification through audio signal measured in sound level meter. My professor asked me to apply my program in a ""simple"" case which is a 10 diameter microwave cooling fan with a hole in one of...

Hi!! I've solve the problem i think. Apparently these strange numbers of frequency where obtained because the sensor is mounted near a phonic wheel with 30 teeth. So the frequency was ~ N*30/60. I'm using N/60 now and the g values are at most 1. thanks for all the help and have a good day!

dawoh, ok the engine is mounted in a support so it can be tested, maybe is absorbing maybe not.but if i assume 100 g's and calculate the displacement out of the frequency, what value should i use? N[rpm]/60 or the values provided in Hz? and is there any typical order of magnitude of...

btrueblood, Yes I did. And I realized something i havn't realize before. The frequency given in Hz for each speed N1 and N2 is not the same as N1[rpm]/60 and N2[rpm]/60. Is much higher! What is the meaning of this?

Hi drawoh! I've used exactly those formulas and then converted from ips^2 to g's but i get values in the order of 100 g's...

*vibration velocity [ips] filtered for N2

Hi! I'm making a work for college which involves analyzing the vibrations of a turbofan engine rotating at 2 speeds, N1 beeing the fan speed and N2 beeing the core speed. The data available to me is a table of the vibration displacement[mils] filtered for N1 and it's frequency, and the...