This article at MIT's website details some of the ways the university's research into hearing could improve hearing aids in the future, in particular researching how the ear distinguishes sounds to improve aids.
So how does that help with hearing aid technology? Well, the research could help develop devices that can focus on a specific range of frequencies (like the range of your companion speaking). I can imagine some kind of control device that could help mute outside sounds (especially traffic!) to focus on specific frequencies.
Read the MIT article for more. (They're the experts!)