Mark,
When you run qmake and then make, you should see, among all of the other output, a series of lines starting "Project MESSAGE:" and printing out some details of packages that have been found (or not found). These are printed every time the top-level Makefile generates a Makefile for one of Sonic Visualiser's sub-projects. The exact set of packages mentioned will depend on the sub-project (e.g. the audioio directory sub-project will call for a lot of audio I/O packages).
Anyway, at some point, and probably at several points, you should see a line saying either
Project MESSAGE: Including PulseAudio support for audio playback
or
Project MESSAGE: WARNING: PulseAudio audio playback support will not be included
If you are seeing the latter, that suggests that the PulseAudio pkg-config definition could not be found. What do you get if you run
$ pkg-config --modversion libpulse
from the command line?
Chris
Chris