These plots show a very narrow band signal at 655 sec flight time. It is seen in ERPA1 and ERPA2 and although it is a much weaker signal, it is clearly present in the V1s wave channel as well.
The interval at 655 seconds is probably the best example with a narrow band signal. There are other examples but not all of them show a recognizable correlation on V1s.
The bursts of modulations in ERPA are seen at about a 20sec period correlated with the payload cone motion.
This plot shows when the bursts occur over the long term. (Very little high frequency modulation is seen before 400 sec or after 1060 secs). The line plot overlay is payload pitch angle. It is clear that although the bursts do not always occur at exactly the same pitch angle, they are correlated with the payload coning. The long term V1S spectrogram correleation isn't as clear but it does show cone correlated bursts at the same times as seen in the ERPA in the region from 560 to 700 seconds.
If you listen to the modulation erpsound.mp3 it seems that the frequency varies with coning in a repeating pattern. This file is made from ERPA1 skin data from 300 to 1100 seconds sped up by a factor of 10. This moves the modulation into the 2KHz region where it is easier to hear (and only takes 80 seconds to listen to). The continuous background buzz is due to the sweep.
