Hello this is my Rx7 Fc Turbo 2 and it does a strange noise at above ~ 4.5 k rpms.
Does anyone know what I can do to fix this problem?

I have bought it recently and so far I have only changed oil.

here is a video of the noise:

 

Maybe noise from one or more of your accessories? Have you tried pulling the belts in an effort to isolate the noise? Here are some items to check: idler pullies, PS pump, fan clutch, etc.

 

Thanks for the reply, I will look into it.

 

Sounds like the belts. The double belts for the water pump/alternator is more likely since it's hard to get exactly the same length belt.