It sounds like I am not the only one. I don't think it is my imagination although attributing it to the high speed driving might be a mistake. It seems as though it has to do with wear.

It is a high pitched whine. Eskimonio describes it well when he refers to it as the "jet noise". Eskimonio is also correct that it happens when LIGHTLY pressing the accelerator. It also happens during regen as mikieboyblue describes.

It has definately gotten louder than when it was new. I am guessing I have no chance of explaining this to a Toyota tech. I would probably end up with more trouble than when I started.