White noise in headphones running linux on a Thinkpad T470s23 May 2018
This has been bugging me for a while, finally took a look today. Under Linux on a Thinkpad T470s I was experiencing a whitenoise/hissing sound whenever I had headphones plugged in, and no app was actively playing sound. It happened under various kernels and distros, and it looks like it happens on other thinkpad models as well.
The culprit seems to be the snd_hda_codec_realtek kernel mod.
To blacklist it:
echo blacklist snd_hda_codec_realtek | sudo tee -a /etc/modprobe.d/sound.conf
After a reboot the crackle and hiss in your headphones should be gone