The Steam Frame has two speakers on each side of your face for vibration cancellation

"In its new Steam Frame VR headset, Valve put dual audio drivers on each side in the included head strap. That puts the audio near your ears while you're wearing it, and in my brief time trying the device at Valve's headquarters recently, I thought the sound was just fine. But the choice to have those dual drivers also helps reduce audio vibrations, which helps the headset with tracking while you're playing games in VR, Valve hardware engineer Jeremy Selan tells The Verge."

"The Frame, like many other VR headsets, uses outward-facing cameras built into the main part of the headset for tracking. However, audio with good bass "induces vibrations into the headset," which can affect that tracking, according to Selan. But on the Frame's included head strap, the dual drivers per side are "mounted opposite to each other," which creates "vibration cancellation inherent in the design." That allows for "better tracking, even with good audio," Selan says."

Valve's Steam Frame VR headset places dual audio drivers on each side in the included head strap, positioning sound close to the ears. The dual drivers are mounted opposite each other, creating inherent vibration cancellation. Outward-facing cameras built into the main headset perform positional tracking. Low-frequency audio and strong bass can induce vibrations in the headset, which can degrade camera-based tracking. The opposite-mounted drivers reduce those vibrations, enabling better tracking even with robust audio. The headset delivers satisfactory sound in near-ear placement. The design is modular, allowing alternative head straps and audio solutions to be used later.

Read at The Verge