Calculating Damping Ratios of a structural response

hi,

i am carrying out tests using tennis racquets to determine the effect of
gripping forces on the structural reponse of the racquet. The test
structure has two accelerometers attached to different locations to
determine the damping at these locations. i am getting a calibrated signal
form each of the in m.s2. I have then produced FFT's, which have been
smoothed using a Hanning window, for both magnitude (m.s2) and dB. I have
produced TimeFFT's (wavelets) for each of the vibration signals.

I would like to calculate the damping for each of the resonant frequencies
present in the signals. I have been using the half power method and the
STFT Q estimation methods. i have a couple of questions regarding my
analysis.

1 - does the half power method have to be in dB or can magnitude be used
also? this goes for the STFT Q estimation aswell.

2 - does the half power method require the FRF or can it be used on a
single FFT?

3 - once i have the Q estimation for the STFT analysis (this is decay in
either db/s or m/s/s), is this enough to show damping or do i have to take
it further?

thanks for all your help




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