People who talk on the phone on public transportation face to get uncomfortable because they are afraid of bothering their surroundings. Also, people eager to become singers are suffering from limited situations such as costs, places, and time due to noise problems. Dongdong blocks users' voice and external noise as if they are in a soundproof booth, enabling smooth calls anytime, anywhere. For example, Dongdong equipped with express buses and KTX premium seats can be used according to users' needs. This noisy is about the size of a pencil in the library even if the person next to you hears the user's voice, and you can talk smoothly at noisy concert halls and factories. It weighs only 70 grams and is removable and hygienic. DongDong has its own soundproof device technology and design structure.