The easy way: Run paprefs, go to Network Server and check Enable network access to local sound devices.
Whenever you SSH with X11 forwarding enabled, PulseAudio programs use X11 to discover your sound server (use pax11publish or xprop -root PULSE_SERVER to see for yourself). Just tell PulseAudio to listen for network connections (paprefs as described above), and all X11 programs will be able to use it.
(Other users will not have access to your sound server, unless you allow it yourself in paprefs. The authentication data is carried over in the X11 PULSE_COOKIE property, or you can copy ~/.pulse_cookie manually.)
Note however, that the PulseAudio stream is not encrypted this way, so it is okay for use at home, but not over the Internet.
The slightly more complicated way: Enable network access as above, but tunnel PulseAudio over SSH TCP forwarding. Use pax11publish to discover your PulseAudio port (usually 4713), connect with ssh -R 24713:localhost:4713, then run export PULSE_SERVER="tcp:localhost:24713". This will be slightly slower due to SSH overhead, but is safe to use over the Internet.