Example apparatus disclosed include means for detecting encoded information present in audio obtained from a media presentation device, means for generating a signature of the audio, and means for determining an on/off state of the media presentation device based on a gain level, the means for determining to determine the on/off state based on the encoded information detected in the audio or the signature generated from the audio. Disclosed example apparatus also include means for crediting a portion of the audio to first media based on the encoded information or the signature, the means for crediting to credit the audio by overriding (i) a first determination that the media presentation device was in the off state during collection of the audio with (ii) a second determination that the media presentation device was in the on state based on the collection of the audio.