I asked liquid audio this question:

Q: can you hear the watermarking?

from liquid audio
...
Hi, again

GOOD quiestion.
I consider my self to have a discerning ear, and I have never heard one.
The techs I talk to say that the bit pattern is so wide-spread (and light), that
it takes software to detect it.

Regards

Richard Scott
Manager, Customer Care
Liquid Audio, Inc.