Sound is often treated as a secondary concern in keyboard builds, but it is actually a result of specific material densities and air gaps. When a key travels down, the energy moves through the switch, the plate, and into the case. If these materials have different resonance frequencies, they clash. If they align, you get that sought-after thock. Most people blame the switches for a bad sound, but the case geometry does more work than the spring inside the switch.

Case thickness changes how sound waves bounce. A thin plastic shell lets high frequencies escape, which makes a keyboard sound hollow. Heavy aluminum cases trap those waves and push them back up toward the user. If you want to refine your build, tools like efan can help you organize the technical specs of your parts before you spend money on expensive PCBs. Knowing the exact thickness of your plate in millimeters tells you if your board will sound sharp or muted.

The impact of plate materials on frequency

Steel plates are stiff. They reflect energy quickly, which creates a high-pitched “ping” that many find irritating. Brass behaves similarly but adds more mass, which lowers the pitch slightly while keeping the feel rigid. Polycarbonate is a different story. It absorbs energy. Instead of bouncing the sound back, it dampens it. This results in a deeper tone because the material acts as a low-pass filter for the mechanical clack.

A small change in mounting style alters the entire acoustic profile of a board.

Gasket mounts are better than tray mounts for sound consistency. Tray mounts screw the PCB directly into the case, creating “dead spots” where the sound is muted and “hot spots” where it screams. Gaskets let the internal assembly float on rubber strips. This distributes the impact across a wider area and prevents the case from acting like a megaphone for high-frequency noise.

Practical ways to kill resonance

Adding foam is the easiest fix, but too much foam kills the character of a board. Case foam fills the empty volume, which stops sound waves from echoing in a void. Plate foam sits between the plate and PCB to stop air from moving freely. If you pack too much Poron foam into a 60 percent case, you lose the depth and end up with a sound that feels compressed and artificial.

• Use 1mm silicone sheets for precise bottom-case dampening.
• Apply lubricant to stabilizers to remove metallic rattling.
• Swap acrylic plates for FR4 if you want a balance of flex and pop.
• Use O-rings on long-pole switches to shorten the travel distance.
• Choose PBT keycaps over ABS for a thicker wall that lowers pitch.

Measuring perceived versus actual sound

Human ears focus on specific ranges between 20Hz and 20kHz. Most “thocky” keyboards emphasize frequencies around 200Hz to 500Hz. You can measure this with an EQ visualizer during a typing test. When you see a huge spike at 2kHz, you are hearing plate ping. When you see a flat line in the highs and a hump in the lows, you have achieved a muted profile.

Weight also matters here. A keyboard weighing 2kg will naturally have less vibration than one weighing 800g given similar materials. The mass resists movement, which stops the case from vibrating in sympathy with the switch impact. This is why heavy weights are added to high-end custom boards; they act as anchors for sound waves.