A disclosed example method involves determining, using a neural network at a stationary unit, a first distance of a first portable audio detector from the stationary unit, the first portable audio detector associated with a first panelist, the stationary unit located in proximity to the media presentation device. The example method also involves determining, using the neural network, a second distance of a second portable audio detector from the stationary unit, the second portable audio detector associated with a second panelist. In response to the first distance being less than a threshold distance, the media is credited as exposed to the first panelist. In response to the second distance being more than the threshold distance, the media is not credited as exposed to the second panelist.