It might be because either your pulseaudio driver is broken and/or has permissions set to root.
I had solved this problem with the following commands :
# clean and reinstall pulseaudio
sudo apt-get remove --purge alsa-base pulseaudio
sudo apt-get install alsa-base pulseaudio
sudo apt-get -f install && sudo apt-get -y autoremove && sudo apt-get autoclean && sudo apt-get clean && sudo sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
# fixes user folder permissions
sudo chown -R $USER:$USER $HOME/
# then reboot
sudo reboot
Pulseaudio should be started at startup but you can manually start it with :
pulseaudio --start
If the problem persists, feel free to paste your system log here
tail -100f /var/log/syslog