Wireless communication technology such as NFC and RFID makes the data transfer between devices much easier. Instead of the irksome typing of passwords, users are able to simply authenticate themselves with their smart cards or smartphones. Relay attack, however, threatens the security of token-based, something-you-have authentication recently. It efficiently attacks the authentication system even if the system has secure channels, and moreover it is easy to deploy. Distance bounding or localization of two devices has been proposed to detect relay attacks. We describe the disadvantages and weakness of existing methods and propose a new way to detect relay attacks by recording a background noise.