Since air is trapped between your head and the diaphragm it creates a pressure zone (even with open-back headphone designs), and as the headphones shift with movement you may hear a slight crinkling sound from the diaphragm. This is a normal occurrence with many headphone driver designs and is nothing to be concerned about - it's the sound of the diaphragm moving back and forth with the changes in air pressure. This noise is usually at a low level and should not be heard above your audio while in use.
Sometimes as the driver is worn in with age or heavy use, the sound can become more apparent, and sometimes it may also lessen again. This is mostly influenced by factors in your environment (such as temperature and humidity), and we don't have control over whether or not this occurs.
We recommend exercising certain cautions when handling your headphones: trapped air can create high pressure and sudden pressure changes could damage the diaphragms by over-stressing them, which is not covered by warranty. When you put the headphones on or take them off, it's not a good idea to press them hard and fast against the head, so we recommend reasonably slow and steady movement to allow the air pressure to stabilize.
If you need further help, please email us at email@example.com and we’ll do our best to assist.