Soft dB Opus Suite Data Logger Module - Manual (Page 31)

30
This parameter allows adjusting the overlap between the time
blocks used for the global levels historic calculation. This
parameter can be adjusted from 0% to 90%. This parameter is
used to increase the number of blocks and the time resolution of
the historic graph. We suggest keeping this parameter to 0% if
standard acoustic signals are used. A larger overlap can be used to
avoid aliasing problem when the signal is impulsive.
The Export .txt function allows exporting the global historic data in text format.
9.1.2 Average FFT
This function computes the average power spectrum for the entire framework of the selected
channel. First, the time signal of the entire framework is divided into blocks of an adjustable number
of samples. The power spectrum is computed for each block and a linear average is obtained. Also,
the Average FFT module allows the overlap of the blocks used for the average. For instance, the use
of an overlap of 66% and the Hanning time window is a classic set-up that compensates for data lost
in the time window.
The interface of the Average FFT function is presented on the next figure.