Is it possible to reduce the noise of an air-to-air heat pump?

I have an air heat pump. One of the best models on the market. My neighbor has a pump from another company, also expensive and recommended. They both hum quite loudly. My brother-in-law also has a loud humming noise. Apparently it's normal and there's nothing that can be done.

Instead of exhaust fumes, will we now have noise pollution? Is there any way to reduce this noise?

It's not terribly loud and I can live with it, but I bought a house near the forest so that I could sometimes be outside in silence. And you can't call it silence.

My neighbor found out and says there are no solutions, but in my opinion there is a solution to everything.

Don't advise me to change my heating system, I don't intend to install gas. I'd rather have the hum of a pump than burn fossil fuels. Someone advised me to install gas, but I spent almost PLN 90 on the pump and photovoltaics.

And just to clarify - I mean, of course, the noise of the unit outside.