CIC Invisible Rechargeable Hearing Aide With Noise Reduction Ear Sound Amplifier Adjustable Tone for the Elderly Free Ship -If you hear a howling,check the ear (silica gel) is appropriate and whether the size of plug is tight, the appropriate choice of earplugs and plugged, make sure no air leakage. -Increase volume gradually to avoid sudden increase in sound. -Choose an earplug of slightly bigger size to avoid whistler. -Adjust volume to the minimum before wearing. About noise , you can do this steps to remove it . That is normally situation that hearing aid make whistle noise . Note USB Cable* 1 User manual in English * 1 Warranty card * 1 Cleaning sweeper * 1 Earplugs * 3 Principal machine * 1 Packing list: Target user: People with moderate to severe hearing lo are available (average hearing lo not exceed 80dB) Product Size: 4.6*3.8*0.9cm Product Weight: 8g Current: 1.4mA Working voltage: 1.5V Standard Battery: A675 button cell Equivalent Input Noise : 30dB Frequency Range:300Hz ~ 3800Hz Harmonic Dist:5% Max Gain:325dB Max Out:1184dB Easy to operate and use. Technical Parameters: Comes with USB charge) Comes with different types of earplugs to fit different ear sizes. Support volume adjustable, easy to adjust the volume to meet your needs.Suitable for the elderly and those people with hearing lo, perfect to help hearing the outside sound again, regaining confidence. It can greatly reduce noise, providing high clear sound quality. The product mini and lightweight, ergonomic design, invisible and comfortable to wear. Intelligent noise reduction. Feature: Company information In 2019, it invested and set up a factory in Xiamen to build a large domestic hearing aid production and r&d base with an area of about 12,000 square meters. Since the introduction of automatic production system in 2018, the company has taken the lead in realizing automatic production of hearing AIDS in China. Accurate automatic operation has greatly improved production capacity and made quality more stable