An acoustic communications network includes acoustic modems that exchange messages on an acoustic communications medium, such as tubing deployed in a wellbore. The acoustic communications medium is characterized by an acoustic transfer function having a plurality of passbands and a plurality of stopbands. The messages are communicated by encoding the message into a plurality of symbols representing the message and distributing the plurality of symbols across a bandwidth of a wideband acoustic signal that spans at least one passband and at least one stopband of the acoustic transfer function.