A method of generating an estimate of background noise in a playback environment, including steps of: during emission of sound in the playback environment, using a microphone to generate a microphone output signal (Mic), wherein the sound is indicative of audio content of a playback signal, and the microphone output signal is indicative of the audio content and background noise in the playback environment; characterized in generating gap confidence values in response to the microphone output signal and the playback signal, where each of the gap confidence values is for a different time, t, and is indicative of a confidence that there is a gap, at the time t, in the playback signal; and generating an estimate of the background noise in the playback environment using the gap confidence values, wherein the estimate of the background noise in the playback environment is or includes a sequence of noise estimates, each of the noise estimates is an estimate of background noise in the playback environment at a different time, t, and said each of the noise estimates is a combination of candidate noise estimates for a different time interval including the time t, wherein the candidate noise estimates have been weighted by the gap confidence values and wherein the noise estimate for each said time interval is generated by: (a) identifying each of the candidate noise estimates for the time interval for which a corresponding one of the gap confidence values exceeds a predetermined threshold value; and (b) generating the noise estimate for the time interval to be a minimum one of the candidate noise estimates identified in step (a). during emission of sound in the playback environment, using a microphone to generate a microphone output signal (Mic), wherein the sound is indicative of audio content of a playback signal, and the microphone output signal is indicative of the audio content and background noise in the playback environment; characterized in generating gap confidence values in response to the microphone output signal and the playback signal, where each of the gap confidence values is for a different time, t, and is indicative of a confidence that there is a gap, at the time t, in the playback signal; and generating an estimate of the background noise in the playback environment using the gap confidence values, wherein the estimate of the background noise in the playback environment is or includes a sequence of noise estimates, each of the noise estimates is an estimate of background noise in the playback environment at a different time, t, and said each of the noise estimates is a combination of candidate noise estimates for a different time interval including the time t, wherein the candidate noise estimates have been weighted by the gap confidence values and wherein the noise estimate for each said time interval is generated by: (a) identifying each of the candidate noise estimates for the time interval for which a corresponding one of the gap confidence values exceeds a predetermined threshold value; and (b) generating the noise estimate for the time interval to be a minimum one of the candidate noise estimates identified in step (a). (a) identifying each of the candidate noise estimates for the time interval for which a corresponding one of the gap confidence values exceeds a predetermined threshold value; and (b) generating the noise estimate for the time interval to be a minimum one of the candidate noise estimates identified in step (a).