A system includes a tubing positionable within a wellbore and a first downhole communication device positionable to receive acoustic signals from the tubing and to transmit acoustic signals to the tubing. The system also includes a computing device in communication with the first downhole communication device and including a processor and a non-transitory computer-readable medium that includes instructions that are executable by the processor to perform operations. The operations include receiving a test message including a spectral waveform from a second downhole communication device. The operations further include determining a desired reception frequency for receiving communications from the second downhole communication device using spectral data generated from the spectral waveform. Additionally, the operations include controlling the first downhole communication device to transmit a response message to the second downhole communication device identifying the desired reception frequency.