question about white gaussian noise

does additive white gaussian noise only change the amplitude of a signal or
does it change both amplitude and phase?

"bamse" <bamse@kyllingen.dkkkk> wrote in message news:<6BEnc.4$NS3.3@news.get2net.dk>...
> does additive white gaussian noise only change the amplitude of a signal or
> does it change both amplitude and phase?

There are two ways of looking at Gaussian noise:

Time domain: Random numbers are drawn from a Gaussian distribution
and added to the samples in the signal, thus "changing the amplitude"
of the individual samples.

Frequency domain: A signal with specified frequency magnitude, given 
by the noise autocorrelation function, and random phase response is 
added to the signal spectrum, thus "changing the phase" of the spectrum.

Rune