1. An apparatus comprising: a speaker; a microphone unit; a control module configured to: produce a pilot tone for output by the speaker within an environment that includes the apparatus; subsequent to producing the pilot tone, generate, by the microphone unit, a first audio signal related to the pilot tone based on sound captured by the microphone unit, at least a portion of the sound comprising the pilot tone as reflected by one or more surfaces within the environment, the first audio signal including one or more characteristics; analyze the first audio signal to determine if the one or more characteristics of the first audio signal have been altered with respect to one or more characteristics of the pilot tone; generate, by the microphone unit, a second audio signal; based at least in part upon the analyzing, at least one of (i) select a signal processing model for performing speech recognition on the second audio signal, or (ii) alter a signal processing model for performing speech recognition on the second audio signal; and perform speech recognition on the second audio signal using the at least one of the selected or altered signal processing model.