High Pitch Noise Generated by Some Heat Pumps / Mini-Split Ductless Air Conditioners

Some heat pumps / mini-split - ductless air conditioners (especially the outdoor unit, but also some of the indoor units) generate a quite high pitch noise when operating. I suspect it is cause by high-frequency switching circuits in the power supply of the unit, as this is a known issue on other electronics like chargers and some electronic inverters that has cheaper components and/or lack glue around some of the components giving off this noise due.

To ask the manufacturers are pointless, they only focus on the noise generated by the fans inside and does not have any measurements of the high pitch noises - a have email many vendors and manufacturers.

Do anyone have any recommendations for units/manufacturers that sells units that do not have (or have very very low) generations of high frequency noise?