Matching

Your mouth is a rather abrupt opening in your face that sounds can emanate from. It is not shaped like the bell of a trumpet or a tuba, which would be more acoustically efficient. Cupping your hands around your mouth, you can form a kind of megaphone that helps your voice carry across greater distances (or noisier environments) than usual. Your ears (at least the weird-shaped fleshy parts on the side of your head) are shaped a bit like the bell of a trumpet or a tuba (on a very bad day), which is very important for hearing. Even so, cupping your hand behind your ear does something similar: it funnels more sound into your ear, helping you to hear even better.

Well, it’s not actually the case that your voice or quiet sounds are amplified or even “funneled” by your hands. It’s more accurate to say that your hands help your mouth or your ear to be better matched to the way that sounds travel through the air. Your cupped hands form an additional interface; a bridge that sound can more easily travel over.

Our hands aren’t optimized for this, of course. They’re not intended for this purpose; our hands are optimized for handling (Ha!) things, not sound waves. Our hands can reach both our mouths and ears and they happen to have useful acoustic properties—even if they’re not really megaphones or ears. It’s interesting that our hands can do this; that we somehow learned to do it at all and that we learn how and when to do it from each other. (An admittedly brief search did not turn up any evidence that other primates do this.)

In any case, cupping our hands can also be a visual cue to others. Holding one cupped hand behind our ear, perhaps craning and turning our head slightly conveys that we’re trying to listen; it’s a universal sign that means, “What? I can’t hear you.” Likewise if someone sees you looking directly at them with your hands cupped around your mouth, they might pay closer attention. (Or even cup their own hand behind their ear to listen!)

Getting your hands involved in this way when we’re trying to be heard or trying to listen necessarily also creates a different posture in us. It focuses our own attention even more because we’re physically more engaged than if our arms simply hung at our sides.

Just as the shape and placement of our hands helps to better match the acoustics of speaking or listening, our posture—our gesture—becomes more of what we’re trying to do. It reinforces the signal being sent to ourselves and others.