To resolve this, please try the following:
Plug your earphones into a different device (phones, music player, etc).
NOTE: Make sure your earphones are completely plugged into the jack.
If the audio from the new device is fine, move the cable gently near the jack and also near the earphones.
If the sounds cuts out or you hear audio interference, then the cable is likely to be damaged. Please see Knowledge Base article 14373 for instructions on contacting Logitech Technical Support.