One of the advantages of cyberware over bioware is the integration of synthetic materials and harder elements. While there are a number of bioware functions which can be mimicked with cyberware - these do tend to be much more invasive however, and thus are usually installed only on Synthmorphs. Other implants are mechanical or electronic elements which can't be replicated with biology - or are paired with extant cyberware. This is the nature of today's implant is along these lines, using elements which are synthetic and may be anchored to other cyberware.
Sound Dampening: This cyberware embedded sound-dampening materials and padding into a bio or synthmorph, primarily in the hands and feet, but it also shields joints, some subdermal areas and extensively works on cybernetic limbs which have mechanical components which may be noisier. This greatly reduces the sound signature of the character as they move, both through locomotion and just flexing or stretching. This implant is quite complex and expensive, but can be a great boon to those who need to move stealthily and avoid being heard. It gives a -20 penalty to all Perception checks to detect the character via hearing, or other audio sensors. [High]
While Sound Dampening has its most obvious use in infiltrators of all stripes, it also has some surprising users - particularly synths or those with extensive cybernetic implants may install this in order to seem more normal or less obtrusive, as it masks unusual sounds produced by the clattering of plastic and metal, the hum of onboard electronics and the noises of mechanical components. However, one does not become stealthier just by installing this mod - it still takes skill and training to move on areas with the lowest sound, carefully place the self as to avoid noise etc. It also helps not to heavily sprint across materials which are not sound dampened, or carry lots of equipment which can rattle around.