Damping

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Various damping techniques

Damping refers to reducing the noise made by a keyboard. There are two points within each keystroke that are inherently noisy: bottoming out (pressing the key all the way down until it comes to a stop, with the sound being the so-called "clack") and when a released key comes to a hard stop in its home position.

Keystrokes can be damped either by using keyswitches with internal damping, or by designing or modifying the keyboard to cut down on sound.

Damped key switches

Prongs

Progs project laterally across the width of the slider.

Vertical dampers

The Alps SKCM Cream Damped and White Damped switches achieves damping by way of small rubber dampers fitted into channels on either side of the slider. The new Matias quiet switch resurrected this idea. With Alps and Matias switches, the rubber blocks are removable, allowing damped switches to be converted to undamped switches; with the "silent" version of Cherry MX, the rubber damper is moulded into the slider and cannot be removed.

Vertical rings

Vertical rings placed on either side of the slider. This is used in the i-Rocks switch.

Horizontal rings and mats

Rubber rings can be placed around laterally around the slider in a manner similar to vertical rings. They can also be placed around the base of the nub that holds the return spring.

Rubber domes

Rubber domes are inherently quiet when bottomed out, as the impact sound is absorbed by the rubber.

External modding

O-rings

Small rubber O-rings can be fitted around a key stem to cushion the impact of bottoming out: Instead of the slider reaching its bottom, the O-ring hits the switch housing.

The effect of using O-rings is a distinctly cushioned landing when bottoming out, when the O-ring makes contact with the switch housing around the slider. The resulting reduced travel (related to the diameter of the O-ring's cross section) and feel is similar to typing on some scissor switch keyboards.

On Cherry MX and clones, O-rings are fitted inside keycap stems against the internal struts in the keycap. Keycaps without internal supports around the stem are not suitable. The O-ring must be pushed some distance up into the keycap, otherwise it completely impedes slider motion.

The thickness of the O-ring should match the keycap used, or it will impede key travel (and feel) too much or not cushion at all.

OEM profile keycaps are typically used with thicker silicone O-rings. WASD Keyboards rate their own O-rings as follows:[1]

Part number Hardness Travel reduction
40A-R 40A 0.4mm
40A-L 40A 0.2mm

Cherry-profile is more often used with orthodontic bands: very thin O-rings originally intended for dental braces. The size to get is 3/16" Medium.

Soft-landing pads

Soft-landing pads are small square pads of rubbery material placed over the top of a switch. The work the same as O-rings except that they are not tight around the key stem.

Silencing clips

A silencing clip works like a soft-landing pad by muting the bottom of the stroke but they also dampen the slider's return. They clip onto pre-existing switches.

Like with O-rings and soft-landing pads, bottoming out is cushioned against internal struts in the keycap which requires that the keycap has them. Both QMX-clips and Zealencios are made for Cherry profile keycaps and would need an additional O-ring for use with OEM profile.

Because QMX-clips and Zealencios surround the tops of Cherry MX switches, thick-walled keycaps work with these clips should be mounted only on key switches with the LED window facing towards the user or else the clip's plastic wall would be in the way and greatly reduce key travel. This means that they are unsuitable together with thick keycaps on many keyboards, including almost all keyboards made for backlighting as those typically have the switches oriented with the LED window facing the other way.

The clips also don't work with clicky Cherry MX Blue or Green because those have small pins in the base of the slider that would get in the way. Clicky clones from Greetech also has those sprues but Gateron does not.

Internal modding

Topre O-rings

A regular Topre switch can be turned into effectively a Silenced Topre switch by placing a thin ring of foam around the slider inside the housing.

One such aftermarket product are the Hypersphere rings [2].

"Trampoline mod"

The bottom of the slider inside a Cherry MX switch is a pin that plunges into a tube. The "trampoline mod" involves opening up a switch and placing a small piece of rubber inside the bottom of that tube.

The original mod used a section cut from an O-ring but silicone balls have been sold especially for this purpose. Clicky Cherry MX switches have different sliders from other variants, requiring different lengths (or number of balls). The mod can be difficult to reverse.

German patent 3742711, filed by Sasse in 1987, describes this and other approaches and depicts them as applied to Sasse series 25 as well as their taller switches.

Latex mod

A small amount of liquid latex "milk" can sometimes be brushed on the inside top of switch housing switch to dampen the sound of the slider's return.

This is often discouraged because latex being a natural material is susceptible to spoiling after a time. Latex is especially sensitive to oils - which could be in lubricants.

Lubrication

Coiled springs can in some instances be lubricated to reduce reverberation. Too much lube on a spring could interfere with the switch's operation and electrical contacts must never be lubricated.

For buckling spring switches, the dental floss mod would be more suitable as it is more easily reversed.

Dental floss mod

Reverberation of buckling spring switches can be reduced by placing a piece of dental floss inside the coiled spring. If done right, it should leave only the sound of the click.

Other

PCB mounting

Plate-mount keyboards hold the switches firm, and effectively amplify the sound of keystrokes. PCB-mount keyboards cut down on the sound by flexing, thereby absorbing the impact of keystrokes.

Some PCB-mounted keyboards can be further damped by placing rubber drawer liner underneath the printed circuit board.

Cushioning under the keyboard

Hard plastic feed on a hard desk surface will amplify the sound of key strokes. Soft rubber feet underneath the keyboard prevents that.

If a keyboard does not have soft feet, the keyboard could be placed onto an extra wide mouse pad or desk pad that would provide some cushioning. Desk pads can be acquired where office furniture are sold. Mousepads that are 60 cm or wider are now getting common.

Reverb

Sound can transfer and reverb inside the voids of a keyboard case. Noise can in some instances be somewhat reduced by filling that void or to reinforce weak parts by gluing a solid rib onto it. Some modders have even put lead weights inside their keyboards to make them more solid.

References

  1. WASD Keyboards — Cherry MX Rubber O-Ring Switch Dampeners (125pcs)
  2. Deskthority thread: Help:Interest Check: Silencing Rings for Topre RF or HHKB