ShanLu ITE Hearing Amplifiers - Aimed at caring Seniors to get Listening a Clear World. Our hearing aids are suitable for person with light or mid hearing loss. It couldn't restore normal hearing, not fit for hearing impairment resulting from organic conditions. As known, feedback or howling can't be avoid for all hearing aids. But we can do proper operating to make it better to decrease noise, whistling. Why there is feedback or howling happened? When you didn't wear the hearing aids well and fully, sound amplified will be out from gaps between ear canal and earbuds, which will be re-amplified again by the hearing aids. Then feedback happened. How to solve the problem? when you are going to using a hearing amplifiers, please select a suitable silicone domes firstly for your ear. When you feel fully but not pain for ear canal, then the silicone domes are ok for you. Please insert the earbuds fully, and keep sound hole at upside position. This to avoid feedback or howling, meanwhile to keep hearing aids from falling off. Most import-please turn on the device only after wearing well. When you don't use it, please turn off the hearing amplifiers and stored into charge case.