Patent ID: 7035700

Claim:
A method for embedding data in audio signals by altering the amplitude of a host signal audio power spectrum, comprising the steps of: inputting a host signal; calculating the discrete fourier transform points for the masking threshold level; computing the masker frequencies and their power levels on a frame-to-frame basis; determining a global threshold of hearing at each said masker frequency on a frame-to-frame basis; obtaining the sound pressure level for quiet, below which a signal is inaudible; inputting a covert signal; digitizing said covert signal; modifying the amplitude of said power spectrum of said host signal by embedding therein said digitized said covert signal on a frame-by-frame basis; inverting the frequency spectrum of said amplitude-modified said power spectrum; obtaining time domain samples for said inverted frequency spectrum; quantizing said time domain samples; transmitting said time domain samples; receiving at a receiver each quantized bit of each said frame of said time domain-sampled said inverted frequency spectrum; processing said each quantized bit to obtain said masking threshold; and recovering data from said embedded said covert signal; wherein said step of determining a global threshold of hearing further comprises the step of computing T Q ⁡ ( f ) = 3.64 ⁢ ( f 1000 ) - 0.8 - 6.5 ⁢ ⁢ e - 0.6 ⁢ ( f 1000 - 33 ) 2 + 10 - 3 ⁢ ( f 1000 ) 4 at each said masker frequency.