MULTIPLE SCRAMBLED LAYERS FOR AUDIO WATERMARKING

Apparatus, systems, articles of manufacture, and methods are disclosed for multiple scrambled layers for audio watermarking. An example system includes a processor to execute instructions to: divide the watermark into a plurality of watermark symbols; map the watermark symbols to a plurality of frequency bins according to a first distribution scheme to create a first watermark layer having a first combination of the frequency bins and a second watermark layer having a second combination of the frequency bins, subsets of adjacent ones of the plurality of frequency bins grouped into a corresponding plurality of frequency clumps; determine a sequence for shifting watermark symbols between the frequency clumps to cause different combinations of watermark symbols that include one watermark symbol from each watermark layer to share up to a first number of frequency bins, the first number of frequency bins to be less than a number of watermark symbols in respective ones of the different combinations; and generate a second distribution scheme to map the watermark symbols in accordance with the sequence.