It seems to be connected to the load on my CPU … I only notice the noise when when suddenly the EVE-Client start to spike 100% CPU repeatedly … when the normal for my computer running 4 Clients is usually up to 30% docked and 60% flying.
A colleague of mine told me that very high and sudden spikes in CPU can cause power supply instability that may cause noise on some motherboards integrated audio solutions.
Other games have not caused this problem with my audio.
Maybe when CCP solves the 100% CPU problem my audio problem may disappear.