-If you hear a howling,check the ear (silica gel) is appropriate and whether the size of plug is tight, the appropriate choice of earplugs and plugged, make sure no air leakage.
Specification:
1.The wire plug connected to the headset.Then earplug connector (hard) to the headset, earbuds (silica gel) to connect to the headphone connector pedestal
2.The battery installation: Gently open the battery compartment cover, put a battery into the battery compartment in the right direction, then close the battery compartment .
3.Before you use this item ,you have to turn the ON-OFF switch to Off,and turn the sound volume to minimum
4.Then put this item on you ear, keep it tightly
5.Next, turn this item ON, adjust the volume until you hear clear sound