Modal Analysis correlations to Acoustics
Modal Analysis correlations to Acoustics
(OP)
I am trying to coorelate the acoustic frequencies taken from impact testing to modes that I got from FEA. How doest the frequencies I measured from impact testing via microphone and oscilloscope coorelate with the frequences in modal analysis. Thanks for your help!





RE: Modal Analysis correlations to Acoustics
What is meant by acoustic frequencies?
Do you meant FRF from impact testing? or measuremnt of sound pressure vs frequency using microphone?
E.Logesh
RE: Modal Analysis correlations to Acoustics
RE: Modal Analysis correlations to Acoustics
What sort of structure are you working on? what frequency range?
By the way, congratulations, an FEAnalyst who does their own experimental testing is off to a very good start.
Cheers
Greg Locock
RE: Modal Analysis correlations to Acoustics
RE: Modal Analysis correlations to Acoustics
Torsional modes will radiate effectively IF the head is not nodal, but it may well be nodal.
I can't imagine that the head itself will have significant modes below 3-4 kHz at least.
Cheers
Greg Locock
RE: Modal Analysis correlations to Acoustics
"I often use a mic as a quick way of instrumenting a complex assembly".
Can I have few information in this regard?
Have you carried out the sound spectrum in narrow band and then compared with the FRF of the assembly?
In my application I have a complex internal sound source covered by approximately spherical encluosure of 3mm thick.
In the assembly I measured the natural frequencies of this enclousre. The sound and vibration generated inside has to pass through the enclosure.I donot know the internal source characteristics.
I want to measure the sound spectrum while this assembly is operating and want to compare with the modal frequencies of enclosure. This is inorder to know which are the significant natural frequencies of the enclosure excited by internal source.
Whether this is a valid approach?
can I have your comments in this regard?
With Thanks and regards,
Logesh.E
RE: Modal Analysis correlations to Acoustics
Then we'd remove, modify, or cover that component and see if we had affected the noise. There are other ways to do this, but this one works, and you can do it by yourself.
Yes, we would often compare FRFs with sound spectrums, in the engine noise lab this was an important part of our source identification technique, since that tells you a lot about the radiation efficiency of each component.
It sounds like you are on the right track.
Cheers
Greg Locock
RE: Modal Analysis correlations to Acoustics
Hello All,
At the moment, Iam using an ANSYS Educational Version
to conduct a Harmonic Acoustic Analysis on
closed cavities (Eg. Simple Rectangular cavity).
I would like to apply a velocity amplitude on pne face of the 2-d rectangular cavity.
I have read through the ANSYS User Guide to perform a harmonic
acoustic analysis, but Iam still not able to apply a 'Velocity
Amplitude' on any face of the cavity (Rather, there seems to be
no options in the GUI to apply a velocity amplitude). #
I would be glad if anyone can help me out
Regards,
Srini
RE: Modal Analysis correlations to Acoustics
Hey rfulky, did you use a FEA software to model your structure? Which one was it? I am interested in doing something similar. I would like to correlate the frequencies measured by a hydrophone to those from the software but I still don't get good results using Femlab. Could you explain me a little more how do you do the modal analysis?
Thank you very much!
RE: Modal Analysis correlations to Acoustics
Please try to create new thread with proper title rather than appending to a thread which is one year old!!!
This will help others to view your thread and answer accordingly.
Don't mind to create new thread if you have query not related to the existing thread.
Cheers
Regards,
Yogesh Birari