I have this great idea: why don't we put a hair dryer in a plastic box and see how many people get cancer from their food?
ETA: HOW DAAARE YOU DOWNVOTE THIS ULTRA-FUNNY COMMENT

69 checking in. Include me in screencap.
There are literally dozens of them.
Sounds like you want small guitar or DJ hardware like: LEKATO Mini Pitch Shifter Pedal to try out the concept. If you have a musician shop in your area, try their selection.
Thousand way to do it, like this: https://play.google.com/store/apps/details?id=com.stonekick.tempo
But most platforms have decent DJ or audio software for this.
Give em a shot. They should work if you pitch-shift them with some simple software to make the 20hz sound like 50hz or whatever.
Tried bone conduction headphones yet?
https://www.techradar.com/news/best-bone-conduction-headphones
We investigated ourselves and found no wrongdoing. Move along, citizen.
Talk to old people. They have time to listen. Delete all social media.
IIRC you're supposed to drink until you urinate in order to confirm proper hydration. Drinking milk until I pee sounds tough.
It's called Romantasy, and it is not the same.
Me too lol