Methods and apparatus to inspect characteristics of multichannel audio

Methods, apparatus, systems and articles of manufacture are disclosed for audio watermarking and, more particularly, methods and apparatus to inspect characteristics of multichannel audio. An example apparatus disclosed herein includes an audio demultiplexer to obtain a first audio subchannel and a second audio subchannel of a multichannel audio signal and a watermark detector to detect watermarks in the first audio subchannel and watermarks in the second audio subchannel. The example apparatus further includes a channel characteristic inspector to compare a number of watermarks detected in the first audio subchannel and a number of watermarks detected in the second audio subchannel to determine whether the first and second audio subchannels were watermarked in accordance with a watermark encoder configuration and a result alerter to distribute an alert in response to a determination that the first and second audio subchannels were not watermarked in accordance with the watermark encoder configuration.