This issue may be related to Syslinux 6.02, which has been identified and fix in the latest ISO. See https://bbs.archlinux.org/viewtopic.php?id=173665 and https://bbs.archlinux.org/viewtopic.php?id=172588 for further information.
See the Wiki page for PulseAudio: https://wiki.archlinux.org/index.php/PulseAudioAnd under installation note pasystray-git. That is an AUR package so you will also want to read up about https://wiki.archlinux.org/index.php/Makepkg and probably want to be familiar with an AUR helper as well. I use https://aur.archlinux.org/packages/cower/ as an AUR helper and think the world would be a