Example 8: A system comprising a first playback device and a second playback device. The first playback device may comprise one or more processors, a microphone array, and a first computer-readable medium storing instructions that, when executed by the one or more processors, cause the first device to perform first operations, the first operations comprising: detecting sound via the microphone array; analyzing, via a first wake-word engine of the first playback device, the detected sound; and transmitting data associated with the detected sound from the first playback device to a second playback device over a local area network. The second playback device may comprise one or more processors and a second computer-readable medium storing instructions that, when executed by the one or more processors, cause the second device to perform second operations, the second operations comprising: analyzing, via a second wake-word engine of the second playback device, the transmitted data associated with the detected sound; identifying that the detected sound contains a second wake word based on the analysis via the second wake-word engine; and based on the identification, transmitting sound data corresponding to the detected sound over a wide area network to a remote computing device associated with a particular voice assistant service. Example 9: the system of Example 8, wherein the sound data further contains a voice utterance and the second operations further comprise receiving at least one message from the remote computing device. The message may comprise a playback command that is based on the voice utterance. In such embodiments, the first operations may further comprise playing back audio content based on the playback command. Example 10: the system of Example 8 or Example 9, wherein identifying the second wake word is (i) based on the transmitted data associated with the detected sound and (ii) without detecting the sound via the second playback device. Example 11: the system of any one of Examples 8 to 10, wherein the microphone array comprises a plurality of individual microphones and the first playback device comprises a voice processor configured to receive portions of the detected sound from respective ones of the individual microphones. In such operations, the first operations may comprise processing, via the voice processor, one or more of the portions of the detected sound to produce the data associated with the detected sound that is transmitted to the second playback device. Example 12: the system of any one of Examples 8 to 11, wherein processing the one or more portions of the detected sound comprises processing fewer than all of the portions of the detected sound. Example 13: the system of any one of Examples 8 to 12, wherein the first operations further comprise spatially processing, via the voice processor, the detected sound based on one or more of the portions of the detected sound. In such embodiments, analyzing the detected sound via the first wake-word engine comprises analyzing the spatially processed detected sound. Example 14: the system of any one of Examples 8 to 13, wherein the first operations further comprise playing back, via the first playback device, audio content, and producing, via the first playback device, at least one reference signal based on the audio content. In such embodiments, the data associated with the detected sound that is transmitted to the second playback device comprises data that is based on the at least one reference signal.