This rechargeable hearing amplifier for seniors offers fast charging and long battery life, with a 2-hour charge providing 30-35 hours of use. The charging case can charge two hearing aids 4 times and takes 3 hours to fully charge. The device features a 5-channel intelligent sound processing system with an easy-to-use touchscreen for volume control. Included are multiple dome sizes to ensure a comfortable and secure fit, reducing feedback and echo. The lightweight and ergonomic design makes it virtually invisible when worn. Some slight whistling may occur if the earpiece doesn't fit properly, but this can be resolved by trying different earpiece sizes. The product comes with a user manual for guidance.Handling feedback noise: Hearing aids for the elderly may produce whistling or feedback when worn, which is not a quality issue but rather a result of improper earbud fit or wearing technique. The hearing aids come with 3 silicone earbuds in different sizes. Choose the one that fits your ear canal best. If you have any questions, please contact us. We are available 24 7 to resolve any issues. Invisible design hearing aid: The hearing aid has a popular design that is suitable for various occasions. Its lightweight and ergonomic design provides a comfortable fit. The portable charging case is lightweight and can be charged anytime, anywhere. Anti-whistle technology: Advanced chips provide a more natural sound. Includes multiple ear dome sizes to ensure a proper fit and prevent whistling. If the earbud does not fit your ear properly, there may be noise. Therefore, we have updated the product to turn on the device 10 seconds after removal from the case, giving you time to wear it and reduce echo. User-friendly design: The 5-channel hearing aid features a smart touchscreen for easy volume adjustment based on the surrounding environment. It requires a gentler touch than previous versions, providing better protection for your ears. Charging time and battery life: The hearing aid can be fully charged in 2 hours and provides 30-35 hours of use. The charging case can be fully charged in 3 hours and can charge the hearing aids 4 times. The hearing aids turn on automatically within 10 seconds of removal from the case and turn off when placed in the case for charging.