A method for inserting a watermark into an audio signal comprising substituting
a noise-like signal portion with a replacement noise-like signal portion, and the
replacement noise-like signal portion is modulated with watermark data. In a preferred
embodiment Perceptual Noise Substitution is used to locate those portions of the
audio signal which are noise-like and which may be replaced by synthetic noise
modulated with watermark data. Advantageously the inventive method results in a
signal having a synthetic noise signal portion which is modulated by watermark
data but which is perceived merely as a noisy signal portion and not as watermark
data carrying. Furthermore, watermarks incorporated by the inventive method may
be adapted to be robust to various audio compression schemes.