Prerequisites: FRF estimation uses an H1 estimator. This estimator is valid when the background noise
is uncorrelated with the input signal. The Source and Receiver signals must be synchronous
(recorded at the same time), have the same length, and have the same sampling frequency. The
Source signal is not affected by any noise present in the signal.
To estimate the FRF:
Open a signal file.
Choose Modules > Frequency Response Estimation from the menu bar.
The FRF dialog box is displayed. The left half of the dialog box manages the
Source signal, and the right half manages the Recevier signal.
Press the ... button in the Source section of the dialog and
then choose From File to load the Source signal from a file, or
choose From an already opened signal to select the signal from a
list of open signals.
Information about the Source signal you selected is displayed in the Source
section of the dialog box.
Press the ... button in the Receiver section of the dialog and
then choose From File to load the Receiver signal from a file, or
choose From an already opened signal to select the signal from a
list of open signals.
Information about the Receiver signal you selected is displayed in the Receiver
section of the dialog box. Once both the Source and Receiver signals have been selected,
the FRF estimation is performed automatically.
To smooth the FRF, press the Calculation Parameters button.
Select a smoothing factor in the Calculation Parameters dialog box
and press the Close button. Available smoothing options are:
None (no smoothing), 1/12th Oct (the
default), 1/6th Oct, and Third octave (1/3rd
Oct).
The smoothing processing applies a moving-average to the FRF curve (gain vs.
frequency) by using an averaging window whose width depends on the frequency. For example,
if you select 1/12th octave smoothing, the averaging window has a size of 1/12th octave
around the frequency. This means that the curve is less smoothed at low frequencies than
at high frequencies.
Press the Display FRF button to open the FRF in a new
window.
The FRF curve is displayed in a new window, as a graph of dB vs frequency. You
can save the FRF from this window by choosing File > Save spectrum as FRF and continuing with Step 2 of Saving the FRF File
