If you are facing problems with sound when using headphones ex: the sound is audible on speakers and headphones at the same time, you can fix it by modifying /etc/modprobe.d/alsa-base.conf.
Determine the chipset using
sudo lshw -c soundDetermine your computer's model details
sudo dmidecodeGo to http://doc.ubuntu-fr.org/audio_intel_hda#acer and find the line you need to add
Take a backup of /etc/modprobe.d/alsa-base.conf and add that line.
Restart the system after you have saved the changes.