Figure 5

Fourier power spectra of the average of frames 1, 11, ..., 191 when spatial phase shift, imposed frames with air bubbles, and additive random noise in 0, 25, 75, and 90% of frames in panels A, B, C, and D, respectively. The actual DF is 0.2 Hz (DP = 5s). As in the Fourier power spectra of Figure 2, split peaks occur about the dominant frequency (panels A and B), and spectral peaks are completely absent at the highest white noise level (panel D). Although there is a peak near the actual dominant frequency in panel C, it is blunted and shifted.