A picture is work a thousand words. So they say. If the neighbour creates noise in the open air, such as repairing motorcars, try and photograph the activity. Better still, videotape will provide both sound and vision at the same time of the noise. In some cases it might be your word against that of the neighbour.
Independent evidence is often crucial.
Try to obtain evidence from visitors to your home who are subject to the noise. People with some form of officialdom, the police, environmental health officers, who have visited you, might provide some cogent and unequivocal evidence of the noise nuisance. If the noise affects other people, perhaps a group of your neighbours, consider banding together in a joint action against the noise creator. A larger group might make more of an impact upon the authorities than a sole individual. You must let you neighbour know of your complaint.