This is usually caused by vibration and bumps being transmitted through the cable. To resolve it, please do the following:
Loop the earphone cables up over the top and back of your ear instead of allowing them to hang straight down. This will reduce or eliminate the noise.
If your earphone cables have a cinching slider, tighten your cable up so as to make contact with your skin.
If you are participating in a sport or other physical activity, run the cable up and over the top of your ear, tighten your cable cinch (if present) and place the cable cinch at the back of your head near the base of your skull.
The preceding actions will reduce or eliminate the vibrations being transmitted to your ears, and should also reduce the rustling and scraping noises.
If the above solutions do not resolve your problem, consult Knowledge Base article 12289 for instructions on contacting Logitech Technical Support.