why does the terminal start pulseaudio?

[Piscium]

I would like to control when pulseaudio runs, and noticed that it was
being started by unknown parties. Digging into that I came up with a
simple test case as follows:
1. on lightdm logged into an openbox session
2. started urxvt
3. confirmed that pulseaudio was not running
4. started the xfce terminal
5. pulseaudio immediately started running.

Why???

[bob at arch-tornado ~]$ ps -e | grep xfc
[bob at arch-tornado ~]$ ps -e | grep pulse
[bob at arch-tornado ~]$ xfce4-terminal &
[1] 720
[bob at arch-tornado ~]$ Failed to connect to session manager: Failed to
connect to the session manager: SESSION_MANAGER environment variable
not defined

[bob at arch-tornado ~]$ ps -e | grep pulse
    727 ?        00:00:00 pulseaudio
[bob at arch-tornado ~]$ ps -e | grep xfc
    720 pts/0    00:00:00 xfce4-terminal

If I log into a xfce session then pulseaudio also gets started even if
I don't start the xfce terminal. In the xfce panel I have a bunch of
xfce plugins configured.

I do not have the xfce pulseaudio plugin installed. I am on Arch Linux.