Data embedding in audio signals

This paper presents results of two methods of embedding digital audio data into another audio signal for secure communication. The data-embedded, or stego, signal is created for transmission by modifying the power spectral density or the phase spectrum of the cover audio at the perceptually masked frequencies in each frame in accordance with the covert audio data. Embedded data in each frame is recovered from the quantized frames of the received stego signal without synchronization or reference to the original cover signal. Using utterances from Texas Instruments Massachusetts Institute of Technology (TIMIT) databases, it was found that error-free data recovery resulted in voiced and unvoiced frames, while high bit-errors occurred in frames containing voiced/unvoiced boundaries. Modifying the phase, in accordance with data, led to higher successful retrieval than modifying the spectral density of the cover audio. In both cases, no difference was detected in perceived speech quality between the cover signal and the received stego signal.