1. One or more computing devices comprising: one or more processors; and one or more computer-readable media storing computer-executable instructions that, when executed by the one or more processors, cause the one or more processors to perform acts comprising: receiving a first audio signal generated by a microphone of a device residing within an environment, the first audio signal including a first voice command from a first user within the environment, the first voice command comprising a first request that the device perform a first operation, the first voice command being associated with a first voice signature; causing the device to perform the first operation at least partly in response to receiving the first voice command; receiving, while the device is performing the first operation, a second audio signal generated by the microphone of the device, the second audio signal including a second voice command comprising a second request that the device perform a second operation related to the first operation being performed by the device, the second voice command being associated with a second voice signature; calculating a similarity between the first voice signature and the second voice signature to determine that the first user uttered the second voice command or that a user within the environment other than the first user uttered the second voice command; causing performance of the second operation at least partly in response to determining that the first user uttered the second voice command; and refraining from causing performance of the second operation at least partly in response to determining that a user within the environment other than the first user uttered the second voice command.