induction stovetops create extremely loud high pitched noises, some get up to 100+ decibels. You can't "hear" it but at higher heat levels you can definitely "feel" it in your ears.
What cars produce ultrasound? I thought radar is used.
One of the references is for a Mercedes system that uses ultrasound
Every single car from every manufacturer that has PDC sensors in the bumper, which are typically visible as 4 circular sensors on the surface of the bumper.
Most cars have ultrasonic sensors for parking and radar for longer range detection, such as cruise control.
I hear some car alarm sensors when passing by, the ones that will trigger when someone is about to park too close and hit the armed car.