Methods and apparatus to identify media based on watermarks across different audio streams and/or different watermarking techniques are disclosed. Example apparatus disclosed herein include a watermark detector to detect a first watermark embedded in a first audio stream, the first watermark including a first source identifier and a first timing identifier, and detect a second watermark embedded in a second audio stream, the second watermark including a second source identifier and a second timing identifier. The disclosed example apparatus also include a controller to associate the first and second watermarks with a media detection event when both (1) the first and second source identifiers match and (2) the first and second timing identifiers are chronologically congruent. The disclosed example apparatus further include a transmitter to transmit the media detection event to a data collection facility.