What is Overlap Processing?
Assume we are collecting and analyzing 10 kHz data with 25.6 kHz sampling frequency, and we wish to calculate a 1 k FFT. The data collection time (also known as Time Window) for collecting 1024 time samples is exactly 40 msec. If the FFT processor calculates and displays a spectrum in 10 msec, then it will sit and wait for 30 msec until the acquisition of the next block is completed. Once the first block is collected, rather than waiting for the next block to be fully collected, we can proceed to calculate a new spectrum by using part of the data from the new block and part of the data from the old block. If the data is stationary, there is no reason why we cannot `mix’ data from the two blocks. With the values given above, we could initiate a new FFT calculation by using 75% of the previous block and 25% of the latest one. We would then be performing what is called 75% overlap processing and our apparent processing time (after the first block) would be 10 msec per spectrum, rather tha
