Your headphones may need periodic cleaning:
Cleaning your headset
Applies to:
Ear tips: Remove the tips from the headphones and wipe them with a damp cloth and mild soap. Allow the tips to thoroughly dry before you put them back on the headphones
Headphone nozzles: Clean exterior only with a soft cloth. Never insert any cleaning tool into the nozzle
Armband: Hand wash. Do not bleach. Do not wring out. Dry flat. Do not iron. Do not dry clean