So… they agitate material using sound to increase the volume of chemicals to smell?

Clever little Airbenders

It’s using the ceiling as a diffuser to soften it. Same way that photographers don’t normally point a light directly at a subject but instead use a diffuser like this

https://www.studiobinder.com/blog/what-is-a-light-diffuser-photography/

I agree that LEDs would probably work better with some kind of frosted glass as a diffuser but there are some high lumen LEDs that would work. They do get warm but not halogen warm.

In the Neutronium Alchemist (or one of the books in the Nights Dawn series) a vampire basically says “I was Muslim but that cross only works if you believe it works”

E.g. it’s the fundamental belief of the person wielding it that has the “psychic” effect on the ghost/vampire/remnant.

Edit: apparently it was a ghost who was Sunni and it’s the belief of the ghost that does it. E.g. why the crucifix had no effect on him but a crescent, for example, may have.