1. An apparatus comprising: a microphone; a processor; and computer-readable media storing computer-executable instructions that, when executed by the processor, cause the processor to perform acts comprising: receiving, from the microphone, a first audio signal including a representation of a first utterance; determining a first similarity score for the first utterance, wherein the first similarity score indicates a similarity between the representation of the first utterance and a representation of a defined word or phrase; determining that the first similarity score is less than a first similarity threshold and greater than a second similarity threshold; setting a temporary third similarity threshold for a defined amount of time, wherein the third similarity threshold is less than the first similarity threshold and greater than the second similarity threshold; receiving, from the microphone and within the defined amount of time, a second audio signal including a representation of a second utterance; causing speech-recognition to be performed on the second audio signal; determining a second similarity score for the second utterance, wherein the second similarity score indicates a similarity between the representation of the second utterance and the representation of the defined word or phrase; determining that the second similarity score is greater than the third similarity threshold; and in response to the determining that the second similarity score is greater than the third similarity threshold, changing a state of the apparatus from a first state to a second state.