Acoustic dampening field

From Halopedia, the Halo wiki

An acoustic dampening field is a technology that can block sounds from the outside within its area of effect. The Hog, the civilian version of the M12 Warthog, features an acoustic dampening field that cancels the road and engine noise entirely inside the vehicle.[1]

The Forerunners possessed a similar technology, an example of which can be found in the Temple of the Abiding Truth in Ontom, Sanghelios. Despite being located in the middle of a city, sounds from the surrounding area are muted once one enters the structure.[2] The interior of the complex also features some form of acoustic dampening, with most sound being effectively absorbed by the walls.[3]