In Qt 5.9.1, the libQt5MultimediaWidgets.prl file has:

QMAKE_PRL_LIBS = -L/usr/X11R6/lib64 -lQt5Multimedia -lQt5Widgets -lQt5Gui -lQt5Network -lQt5Core -lpthread -lpulse-mainloop-glib -lpulse -lglib-2.0

So all applications using the Multimedia Widgets module need Pulseaudio headers installed to compile correctly.

The problem is that Qt Multimedia Widgets has absolutely no code to work with pulseaudio. All code is in Qt Multimedia, and libQt5Multimedia.so.5 is linked dynamically with libpulse.so.0, so that dependency is not needed by any means.

It is added because:

• multimediawidgets.pro has: QT = core gui multimedia-private widgets-private
• multimedia/audio/audio.pri has: QMAKE_USE_FOR_PRIVATE += pulseaudio