The Yate Loon 120mm quiet case fan has a true 28 dB(a) decibel rating - measured in an anechoic chamber using ISO standards. This is one instance where the case fan's decibel ratings haven't been understated by the manufacturer. 

This 120mm case fan is a quiet case fan. Yet, it measures at 46 CFM airflow level and is available at a reasonable price. 

Features: 
* Real Silent, only 28 dB(A) 
* High airflow level, 47 CFM 
* 3-pin motherboard connector / RPM 

Specifications: 
* Model: D12SL-12 
* Air Flow: 47 CFM 
* Fan Speed: 1350 RPM 
* Noise Level: 28 dBA 
* Current: 0.30 Amps 
* Fan Size: 120x120x20 MM 
* Connector: Includes a 3-pin motherboard power / RPM connector.