This paper makes the case for "Room-Area Networks" (RAN), a new category that falls between personal area networks and local area networks. In a RAN, a set of nodes can hear each other only if they are in the same room, broadly construed as being within earshot. We define a RAN abstraction, and we present example applications ranging from social contact management to building automation to gaming where this abstraction will help. The requirements of a RAN are poorly served by current technologies such as Bluetooth, near-field communication (NFC), Wi-Fi, and infrared. Acoustic channels, on the other hand, are well-suited in principle for effective propagation within human earshot and sharp attenuation at room boundaries. We provide a portable reference implementation of an 802.11a-like physical layer for the acoustic medium that works on current mobile devices, with successful communication even in noisy environments at distances over 8 meters.