Yes, you can set tracks you upload to be hidden from your profile.
These can only be accessed w/ the direct URL.
During upload, hit the Advanced settings and set Track Visibility to Hidden.
You can even hide play counts, so if you're sending demos around, that's one less thing to worry about.
Of course, you'll still get that 320kbps hi-fi quality~
Note: As of now, tracks can only be set to private during upload. You currently cannot retroactively set tracks to private after they have been public.
To find all your hidden tracks, go to your Dashboard (audius.co/dashboard).