As we all know, the ear has three parts—the outer part, the middle ear and the inner ear. There are tiny hairs in the inner ear. It is the tiny hairs that receive the sound-waves and then change them into what the brain (大脑) can understand. Exposure to loud noises can damage the tiny hairs and this cause hearing loss (损伤). Usually, this kind of hearing loss can be treated if the noise isn't very sudden and loud. Exposure to loud noise for too long a time can cause lasting damage. People with serious hearing loss may need to have an operation, but even after the operation they may not hear as well as before.