Origin:China MainlandModel Number:G25 Charging Type:Chargeable Maximal Sound Output:118dB 4dB Frequency Range:400Hz-3800Hz Equivalent Input Noise Level: 30dB Input Voltage:AC110-220V Output Voltage:DC5V Specifications: Color: Blue, Beige(Optional) Charging Type: USB charging Maximal Sound Output: 118dB 4dB Frequency Range: 400Hz-3800Hz Equivalent Input Noise Level: 30dB Input Voltage: AC110-220V Output Voltage: DC5V Rated Power Supply Current Consumption: 2mA 1) Why there are some background noise? Actually, it is the electric current sound existing in all good machines. Generally, the higher the power, the greater the static sound. Turning on after put it in ears, then turn up the sound gradually. Generally, You will get used to it after 2-3 weeks. 2) What causes the squeal? If the ear dome is not inserted well into ear canal or air leaks at the ear dome edges, when the device is close to hand or wall, a certain amount of sound will go back into the microphone. The sound is re-amplified which causes that annoying whistle. Try and select suitable ear dome. Put the ear dome into the ear canal and make sure it fits snugly inside. Turning on the device after put it in ears. 3) Why the worked pretty well for a few days but a few days latter them do not work Please make sure the device were fully charged. PLease noticed that the device that you were having problems with. Whether there is earwax on the earplug? Once you cleaned that, they will work better Package Included: 1x Voice Sound Amplifier Device (High Quality Box Package) 1x Plug 1x USB Cable 1x Brush 1x User Manual Quickly Charge Sound amplifier charging about 6 - 8 hours can be full and about 80H+ can be used. hearing assistance devices allows you to easily communicate with others, Provide a "boost" for your better life. Double Noise Reduction Hearing Amplifiers Intelligent audio processing, dual filters, remove all kinds of noise. One button switches three different modes, no matter at home, on the road or in the vegetable market, it can easily reduce noise. Suitable for Left or Right Ear The earplugs are made of soft silicone material, which will not hurt your ears for a long time. The ear hook can be rotated 360, and both left and right ears can be used. Small Size and Easy to Carry Easy to carry where you go. Hard ABS exterior, soft silicone interior. Big enough to hold 2 hearing aids. Keep your hearing aids protected from moisture and debris.