I designed this as a joke gift for an older sibling and it actually amplifies sound pretty well.

Please take care about putting the earpiece too far into your ear. If it's likely to be in the hands of children or drunks, think about making a hole in a cork, rubber ball or something like that and putting it over the earpiece tube to prevent it from going into the ear canal.  Use at your own risk!

Source is included, so please share back any improvements you make, and have fun with it.

Printing Notes

Looks good with metallic silk filament. No supports are required for the bell and tube, but the elbow and earpiece definitely require supports. I used tree supports in Cura 5.1. The walls are thin enough that it will end up being solid.

Assembly/Post Printing

The 4 pieces need to be glued together. I used 5 minute epoxy and it worked out great, also coated the earpiece in epoxy to make it smoother. You can try super glue/cyanoacrylate but there's not really enough surface area for it to hold well – epoxy or other more flexible glues will work better.

Decide whether you want a right- or left-handed ear trumpet and glue the earpiece accordingly.