A phone recording is usually enough to show what you are dealing with, even though it is not an official measurement.

Getting a useful recording

• Record the sound itself. Avoid talking over it.
• Hold the phone still, or rest it on a surface.
• Aim for one to two minutes so the pattern is audible.
• Record from inside the room the noise affects most.

Your phone will not produce a certified decibel reading. That is fine for a first report to your council, which mainly needs to understand what is happening and when.