The audio watermarking method, "the audio watermarking method based on amplitude modification," has been proposed by W. N. Lie as a prevention technique against copyright infringement. We have increased the capacity of watermark information by embedding multiple watermarks. However, the multiple embedding causes the deterioration of sound quality. And hence, we propose the sound quality improvement method focused on the DC component which is not perceived by human ears. From experimental results, we confirmed that the subjective sound quality was improved as the robustness was maintained.%様々な攻撃に対して高い耐性を有する音楽電子透かしとして振幅の増減に基づく音楽電子透かしがLieらにより提案されている．しかし，埋め込み容量を増加させることにより音質が劣化するという問題がある．そこで本発表では，人の耳に知覚されない直流成分に着目した音質改善手法を提案する．実験の結果より，透かしの耐性を維持しながら音質の主観的評価が向上したことを確認した．
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