An apparatus for estimating an overall mixing time, where the apparatus comprises a processing element configured to determine differences between energy profiles of a first room impulse response of the first pair of room impulse responses and a second room impulse response of the first pair of room impulse responses at a plurality of different sample times of the first pair of room impulse responses, set a sample time of the plurality of sample times as a mixing time for the first pair of room impulse responses at which the difference between the energy profiles of the first room impulse response and the second room impulse response of the first pair of room impulse responses is equal to or below a threshold value, and determine the overall mixing time based on the mixing time for the first pair of room impulse responses.