This forum uses cookies
This forum makes use of cookies to store your login information if you are registered, and your last visit if you are not. Cookies are small text documents stored on your computer; the cookies set by this forum can only be used on this website and pose no security risk. Cookies on this forum also track the specific topics you have read and when you last read them. Please confirm whether you accept or reject these cookies being set.

A cookie will be stored in your browser regardless of choice to prevent you being asked this question again. You will be able to change your cookie settings at any time using the link in the footer.

FFT units
#1
Hi there, 

I am not quite sure about the units in the Fourier Transform. What does a.u. stand for? The only a.u. that I know of is A.U., astronomical units... But I doubt that they are the same.

Thanks for your time and the app!

José
Reply
#2
Hi José.
a.u. - arbitrary units. It is when you do not know well units of the original signal. For example for sound when the microphone is not calibrated. When we know the original signal we may use corresponding units. For example for the accelerometer the unit is m/s², so FFT spectrum should have unit m/s² * s = m/s ...
a.u. nevertheless is always valid :o)
Reply
#3
Thank you for answering this, Mikhail. Something has apparently stopped me while preparing in answer that has been pretty much along your lines…

Fourier transforms are not uniquely defined and may vary by a constant factor, so attributing a definite unit to the result does not make much sense.
Reply
#4
Oh! I understand. Thank you for your quick response!

Cheers!
Reply


Forum Jump: