Arctic Introduces Quiet Calm RGB Case Fans with Passive Mode | TechPowerUp
 
ARCTIC, today introduces two new semi-passive case fans. A special 0-decibel mode enables completely silent operation when power is not needed. The P12 PWM PST 0 dB fans are available in two different variants, with analog RGB lighting as well as digital A-RGB. Clever feature for silence lovers: The new semi-passive case fans switch to passive mode when the PWM signal falls below 10 %. This allows silent operation at low load while guaranteeing the highest performance when needed.

At full speed, the hydrodynamic sleeve bearing and the new, rubberized contact surfaces reduce noise levels to a minimum. Plus, form has been considered as well as function: twelve RGB LEDs and a transparent rotor provide even, rich illumination. Thanks to high static pressure, the P12 PWM PST 0 dB fans guarantee efficient cooling, even with increased air resistance. An integrated Y-splitter for fan and RGB connection also make them easy to combine
 
Pricing & Availability

• The P12 PWM PST RGB 0dB is available now at Amazon and at the ARCTIC Webshop starting at a price of € 11,99 MSRP.
• The P12 PWM PST A-RGB 0dB is available now at Amazon and at the ARCTIC Webshop starting at a price of € 12,99 MSRP.
• In addition to the classic single fan, the P12 PWM PST A-RGB 0dB is also available in a convenient 3-pack.

I think the price is quite affordable. The passive mode sounds interesting.