An acoustic network is located in a formation traversed by a borehole having a pipe contained therein. The acoustic network includes a backbone network having a number of backbone modems engaging the pipe and acoustically communicating along the pipe using a first modulation technique. A number of end node modems acoustically communicate using a second modulation technique orthogonal to the first modulation technique. At least one of the backbone modems is a bridge hub modem that is coupled to both the backbone network and an end node modem and communicates with the backbone network using the first modulation technique and with the end node modem using the second modulation technique. The end node modems may have a hibernation mode defined by low energy usage with no transmission or receipt of data, and a transmission mode defined by transmission of data by the end node modem.