This Powertone F-138 In-Ear Hearing Aid is a quality hearing aid which can help you hear the sound clearly and loudly. - Silicone ear pads in 3 different sizes, suitable for any form of ear. - If you hear a howling,check the ear (silicagel) is appropriate and whether the size of plug is tight, the appropriate choice of earplugs and plugged, make sure no air leakage.