Whistling Sound
It means that the hearing amplifier is running. They can't be opened directly by hand. You must ensure that the ear canal and earplugs are sealed while wearing them in your ears,then turn them on and adjust the volume until you can hear the sound.
Noise Problem
1. Ensure that the user tries it out himself
2. First use in a quiet environment to wear and use
3. Choose an earplug that fits closely to the ear canal
Not working
1. Need to fully charge the hearing amplifier
2. Clean the earwax that is blocking earplugs
3. Adjust the volume until you can hear clearly