Yes

Won’t work sadly, the “counter sound” can’t be in phase in multiple locations because of delay and reflections. Headphones can do ANC because the ear is basically a single point so the mic can pick up exactly what you’re about to hear and then compensate.

Using a speaker like that would just create double the leafblower noise.

Extinct!

Basically an exponential function.

Linnutee in Estonian, literally “bird’s path” because of the birds migrating south for the winter using it for navigation.