Realistically what can I do about neighbours extremely noisy aircon unit?

We’ve been here for over a year and never had this issue when the next door neighbours (the owners) lived here. New tenants moved in a month or so ago and their air con unit which is close to our bedroom is extremely loud. It seems to be on 24/7 so from when I wake up in the middle of the night to tend to my kids and throughout the day. I’m wondering if it’s an issue with the unit itself because I don’t believe it should’ve this loud. It’s to a point where I have to have white noise on throughout the night to mask the sound. I’ve spoken to the tenants and they didn’t have much to say and nothings changed. Realistically what can I do?