As with the other fan reviews I've done in the past I used the sound pressure level meter below to test the db rating of the fans at 12v, 7v and 5v.
Due to the sound level meter only registering a db rating of 50db+ I adjust the sampling distance to allow the fan to register on the meter.
When the data is complete I will use a 'damping of sound level with distance' calculator to work out the db rating for a greater listening distance. This will give a clearer understanding of the actual volume of the fans we have here.
For testing I used a hotwired ITX PSU which is a fanless silent model. This will provide power for the fan's without producing any noise interference itself.