Cooling and quieting your home-built PC cannot be solved by simply increasing the number of fans. Rather, interference between fans and imbalance of air pressure inside the case can cause unpleasant wind noise, resonance noise, and dust being sucked into the interior. We will explain airflow design based on thermodynamics inside the case and optimal tuning techniques using BIOS/fan control software.
Positive pressure vs. negative pressure: atmospheric pressure balance that achieves both dust prevention and cooling
Air flow within the case can be roughly divided into two types depending on the relationship between “intake volume” and “exhaust volume”.
- Positive pressure (intake > exhaust): As the air pressure inside the case increases, air is forced out through the gap. Installing a dust filter on the intake fan will prevent dust from being sucked in through the slits and terminal holes, making it most suitable for long-term maintenance-free operation.
- Negative pressure (exhaust > intake): Temporary peak cooling performance is high because hot air is quickly sucked out, but the case becomes like a vacuum cleaner, sucking dust from every crevice, and dust quickly accumulates inside. Conclusion: The golden rule is to set the total air volume of the front and bottom intake fans to a “slight positive pressure” that is 10 to 20% higher than the rear and top exhaust fan air volume.
Fan curve that prevents sudden fluctuations in fan rotation speed, which is the cause of noise
The most annoying thing is not the constant fan noise, but the sound of the fan speed rapidly increasing and decreasing.
- Idle ~ Normal (CPU below 60℃): The rotation speed is fixed flat at 40-50% (around 600-800 rpm). It maintains near-silence during daily web browsing and document creation.
- At high load (CPU over 75℃): Smoothly increases to about 70-80%. Fully opening to 100% is accompanied by harsh high-frequency noise, so it should only be set in emergencies where the temperature is at the limit (above 85 degrees Celsius).
- Hysteresis (Step Up/Down Delay) Settings: By setting a response delay (e.g. 3 seconds up, 5 seconds down) so that the fan does not react immediately to momentary temperature spikes, you can completely eliminate fan whirring noise.
The right person in the right place for anti-vibration rubber dampers and wind pressure/air volume fans
Thoroughly suppress case resonance by placing a pressure-oriented fan on the radiator or the clogged filter surface, a flow-type fan on the exhaust section with low resistance, and a silicone damper on the case fixing screws.