As you may already know, PulseAudio 4.0 stable has been released in the 3rd of June and it is available for download.
Among other features, PulseAudio 4.0 handles better the low-latency requests, brings zsh and bash completion for CLI utilities, fixes the echo canceler infrastructure, sets the default resampler to speex-float-1 for lower CPU usage, et cetera. Read more in the official changelog.
How to install PulseAudio 4.0 on Arch Linux:
For now, PulseAudio 4.0 is available via PPA only on Arch Linux. Do this to install PulseAudio 4.0 on Arch:
Enable the Arch Linux Extra repository:
$ sudo su
# echo -e "[extra]\nInclude = /etc/pacman.d/mirrorlist" >> /etc/pacman.conf
Update the local repositories:
# pacman -Sy
Install PulseAudio 4.0:
# pacman -Sy pulseaudio
How to install PulseAudio 4.0 on other Linux Systems
For other Linux Systems, like Ubuntu, Linux Mint, Fedora, Debian, OpenSUSE and many others, download pulseaudio from here.