8. The device of claim 1 , wherein the dialog system is configured to: determine that the audible speech signal is not understandable; determine that the noise level is lower than a threshold value; and output a request to the user to repeat the audible speech.
1. A device comprising: an audio input to receive audible speech from a user of the device and to receive audible background noise; a sound signal processor to determine a noise level from the received audible background noise; and a dialog system to: receive a recognized speech signal; determine that the recognized speech input is indecipherable; determine that the noise level is greater than a threshold noise level; and output a message indicating that the audible background noise is causing the audible speech to be incomprehensible; wherein the dialog system is configured to: store noise signals received over time; correlate noise signals received over time and failed attempts to interpret received speech signals; and determine the threshold noise level based on the correlation between noise signals received over time and the failed attempts to interpret received speech signals; and use the threhsold noise level to determine that the speech signal incomprehensible.