Frequency dampeners
From The Stargate Omnipedia
Devices installed around the vicinity of the Stargate following the first mission to Chulak. Prior to this time the Stargate would generate a considerable amount of seismic activity, shaking the lower levels of the base and its instruments. Frequency dampeners limit Stargate quakes so that someone standing within the Gate room could not tell the Stargate was shaking.
KEY EPISODE
Solitudes - Daniel Jackson notes that Stargate Command no longer shakes when the gate is dialed due to the installation of dampeners.