Whenever audio starts playing, or stops playing, a 'popping' sound can be heard from my headphones. I am running Elementary OS 0.3.2 Freya, and the issue only happens when I am using headphones. The 'popping' also happens when I plug my headphones in and when wifi has connected or disconnected.
If you happen to be using TLP, this could be caused by TLP's default config turning your audio stuff off when you're not playing audio to save power. I noticed my laptop was doing the same thing while playing audio through my headphone port on battery power. When it was "power saving" I noticed a hissing noise coming from my speakers too.
Try setting the following parameters in
/etc/default/tlp to disable audio power saving:
# Enable audio power saving for Intel HDA, AC97 devices (timeout in secs). # A value of 0 disables, >=1 enables power saving (recommended: 1). SOUND_POWER_SAVE_ON_AC=0 SOUND_POWER_SAVE_ON_BAT=0 # Disable controller too (HDA only): Y/N. SOUND_POWER_SAVE_CONTROLLER=N
Then restart the tlp service:
sudo systemctl restart tlp