What is the name of this type of treatment in video/audio?
It's also known as having an solid understanding of microphones and recording techniques, as well as sound audio editing principles. These types of videos are a great example of how awesome sound recording can enhance picture, and examples of the reason no filmmaker should skimp on sound. It's easier to mess up good sound for dramatic effect (say, adding EQ for distortion or making it quieter and adding reverb to make it sound farther away), but near impossible to clean messed up sound to make it usable.