Noise generation in the ventilation system

Hello,
I have the following problem:
We have a single-family house with 170 sqm of living space plus 55 sqm of basement. The whole thing is ventilated with a Wolf CWL 400 ventilation system.
Currently, three of us live in the house. My wife works Monday to Thursday until 3 pm, after which our child also comes home.
This means that from Monday to Thursday between 3:00 pm and 7:00 am, 2-3 people are present, on Fridays two people continuously, and on weekends three people.

In the morning, we ventilate the sleeping area and the bathroom additionally manually. Cooking fumes are blown outside via an extractor hood. There are no special sources of odors.

The system is set so that 125 cbm/h is circulated at night and 230 cbm/h during the day.
It should be said that the sleeping area has a relatively large volume due to an open attic. Nevertheless, the air feels stale in the morning.
The ventilation system cannot be set higher at night because the noise level would otherwise be disturbing.
During the day operation, the ventilation is audible, though not particularly disturbing. However, it is quite loud, especially in the kitchen. This surprises me because, in terms of capacity, up to 400 cbm/h would be possible, but that would already be very loud and disturbing.

Now my question: Is the system set too low at night? Too high during the day? Is the noise perception normal at this "low" level? I somehow have the feeling that especially the exhaust valves are very noticeable and the supply air is quite quiet.

You have to ask this question to the person who sold and installed this system for you.

"Consumed" does not have to mean unhealthy. Do you have the chance to measure/track the CO2_Entwicklung in the bedroom once?

I would just tilt the window in the bedroom, just like in the old days...

First of all, buy a measuring device to test what the air quality values actually are … then you can look further …

you have to ask this question to the person who sold and installed this system for you.

He is asking about experiences, he will get them here. As others say, measure the CO2 level and then retrofit silencers, at least in the bedrooms if the values are not okay.