The difficulty that you have here is that if the local council have confirmed that it complies with regulations, all you can do, in my opinion, is chase the environmental officer to make numerous visits or even install a noise detector to ascertain the level of noise emanating from the unit.
Until you have the evidence and support of the local council, I am of the opinion that you will have a difficult time of convincing the local council to take further action.
I hope this answers your question. If so, kindly rate the answer and provide feedback.
If you have any further questions, please do not hesitate to ask.
To be completely honest, I cannot say. I have not had details of specifications etc and even then, I'm not an engineer do would only be guessing.
I can only suggest that you get on to whoever you can at your local council and make a bit of a nuisance of yourself regarding the issue.
Hopefully you will be able to get the environmental health department to take some forms of action.