Let's split it up into DMUs and EMUs. People can do coaching stock if they like but personally I've never been able to perceive a difference between one type of coaching stock or another. Quietest EMU for me would be the Class 390 by a large margin. Quietest DMU is harder but I'm going to go with the Class 180. Noisiest DMU is fairly obvious to me - Class 142. Noisiest EMU I'm going to go for Class 508 but I don't have a lot of experience with other older EMU types.