THX是一种对电影、电影播放设备、电影播放环境等的认证标准，由卢卡斯影业（Lucasfilm）制定。THX是Tomlinson Holman Experiment的字头缩写，主要为剧院、家庭影院、多媒体产品所设计的品质保证。THX的最终目标是保证在所有获得THX认证的系统上，能够提供一致的体验。比如说一部电影，不论是蓝光影碟还是电影胶片，不论在电影工作室、电影放映厅，还是家庭影院中，都能达到一致的画面和声音的感受，画面的对比度、色彩，声音的响度、频率范围上都能达到很高的一致性。THX标准与国际标准不同，大多数标准都有一个允差范围，但THX不设允差，只有一个最低要求，必须超过才能合格。THX不光是对设备的认证，更包括了对环境噪声和室内空间频响的要求，最新的一些THX前级可以自动地对不同房间做测音和频响补偿。最近THX还在开发Steerable Line Array technology（可控线性阵列），通过DSP调节几十个扬声器组成的整列，THX宣称这样能控制房间的声场，从而能使不同位置都能获得最佳的听音效果，即在同一个房间里能产生很多“皇帝位”。

THX Ltd. is an American high-fidelity audio/visual reproduction standard for movie theaters, screening rooms, home theaters, computer speakers, gaming consoles, and car audio systems. They have certified video games as well. The current THX was created in 2002 when it spun off from Lucasfilm Ltd. THX was developed by Tomlinson Holman at George Lucas' company, Lucasfilm, in 1983 to ensure that the soundtrack for the third Star Wars film, Return of the Jedi, would be accurately reproduced in the best venues. THX was named after Holman, with the "X" standing for "crossover" as well as in homage to Lucas's first film, THX 1138. The distinctive glissando down to a rumbling low pitch used in the THX trailers, created by Holman's coworker James A. Moorer, is known as the "Deep Note".