Watermarking of speech signals based on formant enhancement

This paper proposes a speech watermarking method based on formant enhancement. The line spectral frequencies (LSFs) which can stably represent the formants were firstly derived from the speech signal by linear prediction (LP) analysis. A pair of LSFs were then symmetrically controlled to enhance formants for watermark embedding. Two kinds of objective experiments regarding inaudibility and robustness were carried out to evaluate the proposed method in comparison with other typical methods. The results indicated that the proposed method could not only satisfy inaudibility but also provide good robustness against different speech codecs and general processing, while the other methods encountered problems.