A robust watermark embedded into a Direct Stream Digital (DSD) audio
signal including a flat frequency response in a specific frequency range
which does not extend below 20 kHz or above 100 kHz. The watermark is
therefore hidden in the noise spectrum of the DSD signal, such that the
watermark is inaudible to a listener. Since the noise spectrum contains
important information that helps provide the DSD signals with sharp
transients and an accurate impulse response, the watermark cannot be
removed from the DSD signal without causing significant degradation to
the signal's audio quality.