i already had 2 separate holes in my wall leading to the outside... all exhausted air is going outside and i have a tube connected to the hole which brings cool air in...

my extractor that pushes air through the cool tube extracts at 187 m3/h (meters cubed per hour) extract rate.

187 is low isnt it? i want to get the RVK 150E2-A1 which is- Flow extraction: 420 m3 per hour .. but it should very loud! and i cant have it this loud!... i have a silencer too but i think that the device will be humming loud!