Modification of bit values of samples in accordance with data to be embedded in audio steganography can have high payload at low complexity. Index of the bit modified in the stego signal, however, has a tradeoff with imperceptibility and robustness: hiding data at a lower bit index of samples has low audibility of change with high susceptibility of being affected by intentional or other alterations to the stego.
By choosing cover samples that are above a threshold, in this paper we show that the embedding bit index can be raised reasonably with minimal change to noticeability of stego. Additionally, the threshold for embedding results in a stronger key for data hiding and oblivious retrieval. Measures using spectrograms and spectral distortion confirm the imperceptibility of the stego.