Methods and apparatus for crediting a media presentation device are disclosed. Example apparatus disclosed include a signal generator to compute a signature from audio obtained from a media device during a time period, and an on/off detector to determine an on/off state of the media device based on a gain level applied by an automatic gain controller during collection of the audio. Disclosed apparatus also include a location creditor to credit the media device with presenting media during the time period when the signature matches at least one of a set of reference signatures and the on/off state is determined as the on state or as the off state, the location creditor not to credit the media device with presenting the media when the signature does not match at least one of the set of reference signatures and the on/off state is determined as the off state.