Methods and apparatus for encoding an arbitrary digital message, e.g., a
watermark, into a speech signal are provided. In one aspect of the invention, a
method of embedding digital information in a speech signal comprises the steps
of: (i) generating a spread spectrum signal, wherein the spread spectrum signal
is representative of the digital information and further wherein the spread spectrum
signal is within a frequency bandwidth corresponding to speech; and (ii) embedding
the spread spectrum signal in the speech signal. By making use of spread spectrum
technology and speech analysis techniques in the signal generation and embedding
operations, respectively, significantly higher bit rates can be embedded into the
speech signal without effecting the perceived quality of the recording. The invention
also provides methods and apparatus for recovering the digital information embedded
in the speech signal.
