When customers use a tailgate (or trunk), some systems such as power tailgate and smart tailgate have been introduced and implemented for improving convenience. However, they still have some problems in some use cases. Some people have to search for the outside button to open the tailgate, or they should take out the key and push a button. In some cases, they should move their leg or wait a few seconds which makes some people feel that it is a long time. In addition, they have to push the small button which is located on the inner trim in order to close the tailgate. This paper proposes a new tailgate control technology and systems based on acoustic patterns in order to solve some inconvenience. An acoustic user interaction (AUI) is a technology which responds to human’s rubbing and tapping on a specific part analyzing the acoustic patterns. The AUI has been recently spotlighted in the automotive industry as well as home appliances, mobile devices, musical instruments, etc. The AUI is a technology that can extend to rich-touch beyond multi-touch. The AUI can be easily applied and adapted even to the systems which need a large touch recognition area or have complex shape and surface. This paper addresses how to recognize the users’ intention and how to control the tailgate using acoustic sensors and patterns. If someone who has the smart key wants to open the tailgate, he or she only needs to knock on the outer panel of the tailgate twice. When they want to close the tailgate, just touching anywhere of the inner trim of the tailgate will do. Various digital filters and algorithms are used for acoustic signal processing, and the effectiveness of the proposed methods is shown by a real tailgate system with a micro control unit. Finally, we suggest other applications of vehicles which use AUI technology.