Io the past few years, several algorithms for audio
watermarking have been presented. In a number of algorithms,
watermark embedding and detection were carried out using
spread-spectrum (SS) method. Pseudo-noise (PN) sequence
can be added to the host audio samples in time domain [1,2],
to FFT coefficients [3-61, in wavelet domain [7] or to cepstral
coefficients [SI. Watermark is spread over a large number of
coefficients and distortion is kept below the just noticeable
difference level (JND) by using occurrence of masking effects
of the human auditory system (HAS). Change in each
coefficient can he small enough to be imperceptible, because
correlator detector output still has a high signal to noise ratio
(SNR), as it de-spreads the energy present in a large number
of coefficients.