One or more delay estimators are used to detect failure in a signal processing component, such as an acoustic echo canceller. A first delay estimator is used to generate i) an estimated post-processing delay between when a known audio signal was conveyed to a loudspeaker, and when a portion of the processed audio signal that includes the known audio signal was output from the signal processing component, and ii) a confidence level for the estimated post-processing delay. A failure of the signal processing component may be detected in response to the estimated post-processing delay exceeding a threshold. A second delay estimator may also be used to generate an estimated pre-processing delay and a confidence level for the estimated pre-processing delay for comparison to the estimated post-processing delay and confidence level for the estimated post-processing delay in order to provide further failure detection accuracy and specificity.