Has anyone else mentioned this?
I have a 2024 Ford Maverick hybrid, and whenever I accelerate from 20-30 mph, I keep hearing what sounds like distant sirens. Almost every time, I find myself looking around for an ambulance, fire truck, or police car.
Indeed, it is typical. After our EcoBoost was totaled, we recently converted to a hybrid, and at first, I believed I was constantly hearing sirens from a distance. 
Yes, that is the hybrid system operating as intended. Although it can be rather disturbing, even light conversation can block it out.
When I accelerate hard, my Hyundai makes a faint noise that sounds like a cackling elf. I swear I am not imagining it.
It is the sound used to warn onlookers when a car is coming. Most likely, no one would hear the electric motor. Different, yet similar to the backup warning sound.
Once you hit a certain speed, it stops.
You can use one of these to disable it: Ford PSBK-ECE: https://www.megaohmmotorsports.com/product
Reaching the plug-in place is a bit of a pain, though. Take note.
I am pretty sure there’ is nothing wrong with the speaker.
After installing 493,859 aftermarket stereos, I can confirm the ignition noise does not sound like a siren and isn’t restricted to a specific RPM range.