Example apparatus disclosed herein are to identify encoded information present in audio obtained for a time period. Disclosed example apparatus are also to generate a signature of the audio for comparison with signatures of reference media. Disclosed example apparatus are also to generate a first determination that a media presentation device was in an off state during a first portion of the time period based on a gain level applied by an automatic gain controller to collect the audio. Disclosed example apparatus are also to override the first determination that the media presentation device was in the off state during the first portion of the time period with a second determination that the media presentation device was in an on state during the first portion of the time period, the second determination based on at least one of the encoded information or the signature.