This one is strange. If you think "brainstorm" you hear "brainstorm", and if you think "green needle" then you hear "green needle".

https://www.telegraph.co.uk/news/2018/05/18/brainstorm-green-needle-latest-audio-riddle-tricks-brain/

Works on me every time. I can make it flip back and forth at will.

Your thoughts?
-John