Sorry but I have to disagree
Sorry but I have to disagree with your comment as I am a licensed mechanical engineer who is well versed on ‘mechanical movement’ or more correctly stated automotive acoustics. When I first heard this backup ‘noise’ I questioned the integrity of the drivetrain as most knowledgeable others have done. After thinking about what could be making the ‘noise’ I concluded there was something wrong or it was intentionally being made. After hearing it on other hybrids I concluded that the ‘noise’ was a poor attempt to be a warning noise. You obviously have a superhuman hearing ability to differentiate sounds that you want the world to know by belittling those who don’t. I feel sad for you.