Switched the cooker fuse off. Removed the oven. Jiggled a wee bit the cables to check if they are tight – they were. Switched the fuse on and the hob doesn’t make the crackling sound any more (on all for rings)! To be honest I have no idea what was wrong but I think that simple switching fuse off and on again would fix the problem. Thanks!
https://i.ibb.co/Z6LVqs2/picture.jpg
Update: The problem came back.
It has stopped making noises. Don’t know what’s going on to be honest.