Speech dialog system, comprising: - a speech recognition unit recognising a user's speech input, - a speech output unit outputting speech to the user in response to the user's speech input, - a speech output control unit controlling a play back mode of the speech output to the user, - a detector detecting information from at least one of the speech input unit and a sensor detecting information about the surrounding of the speech dialog system, wherein the speech output control unit adapts the play back mode of the speech output unit in dependence on the information received from the detector.