哈斯效应（英语：Haas effect; Precedence effect）是一种双耳心理声学效应，声音延迟对人类方向听觉的影晌要比音量大小的影晌大得多的效应。故此，它也被称为优先效应。第一声音发出后，延迟25-35毫秒内接着发出第二声音，听者则能听出为一整体融合的声音；但若延迟时间超过35毫秒，听者则听出为第二声源。听者也以第一声音为主确定声源的地点和方向。 哈斯效应是亥尔姆·哈斯于1949年在他的博士论文中描述的。 利用哈斯效应对调整会场和音乐厅整体声音和谐是很重要的。

The precedence effect or law of the first wavefront is a binaural psychoacoustic effect. When a sound is followed by another sound separated by a sufficiently short time delay (below the listener's echo threshold), listeners perceive a single fused auditory image; its perceived spatial location is dominated by the location of the first-arriving sound (the first wave front). The lagging sound also affects the perceived location. However, its effect is suppressed by the first-arriving sound.