Yes - noise can be dangerous. If it is loud enough and lasts long enough, it can damage your hearing. The damage caused by noise, called sensorineural hearing loss or nerve loss. When noise is too loud, it begins to kill the nerve's endings in the inner ear. As the number of nerve endings decreases, so does your hearing. There is no way to restore life to dead nerve endings, the damage is permanent.
Ear infections are not contagious but are often associated with upper respiratory tract infections (such as colds). Such an infection causes swelling in the lining of the nose and the natural drainage pathways of the ears (the Eustachian tube), which makes ear ventilation worse and makes an ear infection more likely.
The ear has three main parts: the outer, middle, and inner ear. Any source of sound sends vibrations or sound waves into the air. These funnel through the ear opening, down the ear canal, and strike your eardrum, causing it to vibrate. The vibrations are passed to the small bones of the middle ear, which transmit them to the hearing nerve in the inner ear. There, the vibrations become nerve impulses and go directly to the brain, which interprets the impulses as sound: music, a slamming door, a voice, etc.
Yes, and airplane travel can be made immediately. One of the additional advantages of tube placement is that the ear pain of takeoff and landing will be eliminated. With tubes in place, the pressure equalizes instantly, and no pain should be felt unless the tube has become clogged.