high volume flow rate

[cakabo28]

hı everybody,
I have to use cross fan has high volume rate for split type indoor unit.Yes I have it,my old volume flow rate was 750 m3/h and now new volume flow rate 850 m3/h.
but at the same time noise has increased together with volume flow rate.The noise like whistle...
Please help me.
what can ı do?

[750 Valve]

Is a lower fan speed possible? Noise is likely additional static pressure.

[cakabo28]

unfortunately rpm must be constant.

[Brian_UK]

Then check for uneven surfaces, jet nozzle effect and vibrating surfaces or edges.

Think of a high wind blowing through an almost closed door - it whistles.

[cakabo28]

But whistle occurs when air passing through evaporator.
and ı want to learn what the static pressure is.

[Magoo]

Hi
sounds like a trunk duct design with constant fan speed and constant supply duct static pressure. If noise is from the air handler then the clearance between the fan tips and scroll are too close, if the fan motor has recently been replaced the clearance may have been changed and the air discharge is acting like a siren.
regards Magoo