meling c600 hearing amplifier rechargeable digital personal hearing aids noise cancelling,sound amplifier devices with charging box pair meling whstling&feedback<br> a)the volume is too lou<br> to solve this, please turn down the volume to a suitable level.<br> b)the user is putting pressure on the microphone<br> it's very common to experience whistling or feedback while inserting the device in the ear. this is because there is pressure on the microphone dont worry, once you have the device securely fit in your ear and remove your hands from the device, the whistling will stop.<br> c)you are not using the correct size earplugs. please choose a suitable earplug and try again.<br>