The actual sound pressure ratings of the systems vary from manufacturer to manufacturer. However as a rough guide to sound levels:

A typical indoor unit will operate at levels of around
26 db when in its quietest ‘mode’.

To put this into context:

An empty studio is typically around 20 db and a library 40 db. In short modern air conditioning units are quiet.

The outdoor units have anti vibration systems, quiet fan motors and compressors to ensure that they run as quietly as possible.

Your account handler will be able to provide you with the DB ratings of your chosen equipment should you require them.