6. A non-transitory computer-readable storage medium storing instructions that when executed by a processor cause the processor to: receive a first audio signal including a representation of a first utterance; determine 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; determine that the first similarity score does not satisfy a first similarity acceptance criterion and does satisfy a second similarity acceptance criterion; modify the first similarity acceptance criterion for a period of time; receive a second audio signal including a representation of a second utterance within the period of time; determine 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; and change a state of an electronic device based at least in part on a determination that the second similarity score satisfies the modified first similarity acceptance criterion.
6. A non-transitory computer-readable storage medium storing instructions that when executed by a processor cause the processor to: receive a first audio signal including a representation of a first utterance; determine 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; determine that the first similarity score does not satisfy a first similarity acceptance criterion and does satisfy a second similarity acceptance criterion; modify the first similarity acceptance criterion for a period of time; receive a second audio signal including a representation of a second utterance within the period of time; determine 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; and change a state of an electronic device based at least in part on a determination that the second similarity score satisfies the modified first similarity acceptance criterion. 10. The non-transitory computer-readable storage medium of claim 6 , wherein the first similarity score is determined based at least in part on a comparison of the representation of the first utterance and the representation of the defined word or phrase.