NIHL is a hearing loss that is usually often permanent loss. Harmful levels of noise cause this hearing loss. Most often this happens in both ears equally, but depending on the noise, this can also happen in one ear. Noise exposure can come from loud, sudden sounds such as blasting or firearms, or from constant harmful levels for a prolonged time, such as working in a factory or around machinery. Think of your ears as a speaker. If you turn up the volume up too much it will blow the speaker making sounds distorted.