As you get older, it will eventually become harder to sort out the voices of your friends and family from the background noise of a busy restaurant.
But at any age, you can confirm by experiment that this can be compensated for by cupping your ears with your hands to gather more sound from directly in front of you and to block out the sound from other directions. The voice of the person on the other side of the table will jump out at you.
I’m told that one of my grandaunts, who was nearly deaf since youth because of an accident, would use an ear trumpet. It wouldn’t surprise me if there were also some much smaller old-timey device to mimic the effect of cupping your hands, but I’ve never seen one. Ear trumpets were made obsolete by electronic hearing aids, but “ear blinders” (like the eye blinders they make horses wear) could help a lot of people today.
Sadly, I’m also told that, because of vanity, almost nobody would wear ear blinders in public, even if they were made of transparent plastic, with the evidence being that many seniors are reluctant to wear hearing aids. Maybe alone at home watching television they wouldn’t be embarrassed, but for that scenario they’re used to just cranking up the volume. I should never underestimate the power of foolish vanity, yet if people will happily wear Skullcandy over-ear headphones or Google Glass, why not transparent ear blinders? (Maybe fluorescent colors instead?)
For a science fair project, it would be interesting to experiment to find the optimal shape for such ear blinders. You could fabricate various shapes on a 3D printer until you converge on a great design. And you could do some field tests with real seniors. And what’s the most comfortable way to wear them — like over-ear headphones, like Bluetooth headphones, or something else?
Summary: As one ages it becomes harder to hear conversations in noisy places. Cupping the hands to gather more sound from in front and to block sound from other directions can compensate for this, but nobody wants to hold their hands up to their ears the whole time they’re eating. Use a 3D printer to build a small, wearable device that optimizes this effect, and field test it on seniors.