Welcome. The Venza will make that noise when backing up as long as the ICE (internal combustion engine) is not running and is in the "EV" mode. Your Venza will make that noise under 20 mph even going forward in EV mode, which would be ICE is not running.
Enjoy, and as time permits, that a look through your owner's manuals. There's ALOT of info that may seem over whelming at times.

 

our '24 Venza Limited makes a very quiet standard electronic vehicle sound. I have to roll the windows down to hear it and, even then, it seems quiet. The Honda CRV hybrid is LOUD at slow speeds, forward and reverse, and the Rav4 hybrid make a really loud electronic noise below about 20 MPH. Our Venza, even when in electric mode, stops making the sound at around 12 mph.

The regulation in a nutshell: "the National Highway Traffic Safety Administration issued its final ruling in February 2018. It requires hybrids and electric vehicles traveling at less than 18.6 mph (30 km/h) to emit warning sounds that pedestrians must be able to hear over background noises."
And: "The vehicle must make a continuous noise level of at least 56 dBA (within 2 meters) if the car is going 20 km/h (12 mph) or slower, and a maximum of 75 dBA."
So there is some variation in how loud the sound is required to be.

 

The "EV sound" is loudest when in reverse. I'm usually in battery mode when in reverse and you should be able to hear it.

 

I am talking about reverse hybrid noise.
My 24 venza is super quiet either ev mode or engine mode.

 

If your Venza does NOT make ANY sound matching what's in that video, something is not working properly. To my knowledge, you cannot shut it off. It is a safety feature as the guy says in the video.

 

I notice running over fire hydrants, dogs, goats, low posts, curbing, 🤣 🤣 Be sure to turn on all the safety features that you have access (Parking assist, auto stop forward and backwards etc).

All of ours over the years have done this. Also, at slower speeds I can hear it in forward drive! Sounds like an alien spaceship approaching.

812347-minimumsoundrequirements.pdf (nhtsa.gov)

Federal Government Places Sound Requirements on Hybrid and Electric Vehicles - Las Vegas Injury Attorneys | Henness & Haight (hennessandhaight.com)

Be advised people walking in the street with non-hearing aid devices in their ears have a death wish.