Jonsbo ( Jonsbo CR-1000 EVO )

The Jonsbo CR-1000 EVO "Silent Series" incorporates several design features intended to produce a low-noise profile while maintaining cooling efficiency. However, the measured noise level of 22–32 dB(A) means it is not completely silent, with noise increasing as CPU load and fan speed rise. 

Low-noise design features

• Acoustically-optimized fan blades: The included 12cm PWM fan has nine sickle-shaped fan blades that are designed to maximize airflow while minimizing turbulence, a common source of fan noise.
• Hydraulic bearing: The fan uses a durable and quiet hydraulic bearing, which has a longer lifespan and generates less friction and noise than standard sleeve bearings.
• Vibration-damping pads: Eight shock-absorbing silicone pads are fitted on the fan to reduce vibrations, which helps prevent rattling and further lowers noise output.
• Pulse-Width Modulation (PWM) control: This feature allows the fan speed to be dynamically controlled by the motherboard based on the CPU temperature. The fan can spin at lower RPMs when the CPU is idle or under low load, significantly reducing noise. 

Factors affecting noise levels

• Fan speed: The cooler's noise is directly tied to the fan speed, which can range from 600 to 1500 RPM. At lower speeds, the noise is minimal, but under heavy CPU load, the speed—and consequently the noise—will increase.
• CPU thermal design power (TDP): The cooler is rated for up to 220W TDP. If your CPU's power draw pushes close to or exceeds this limit, the fan will have to spin at maximum speed, producing more noise to maintain acceptable temperatures.
• Case airflow and ambient temperature: The cooling performance and noise of any CPU cooler are also affected by the overall airflow and temperature inside your PC case. Poor case ventilation can cause the CPU cooler to work harder and louder.