The inner ear can be damaged by exposure to loud noise. This damage is sometimes referred to as "acoustic trauma".

Acoustic trauma may result from exposure to very loud short burst of noise, like gun shots or explosions, or it can result from longer term exposure to lower volume sounds from concerts, machinery, loud stereos etc.

A typical early warning symptom from such exposure is temporary hearing loss and tinnitus. But, if the exposure is loud enough or long enough, the hearing loss and tinnitus can be permanent.

The damage can also be gradual, so it's hard to notice it's happening.

If you like being able to hear, you should definitely protect your hearing from exposure to loud sounds. Wear hearing protection when using noisy equipment like chain saws, leaf blowers, lawn mowers and other such devices. Avoid extended exposure to very loud entertainment like concerts, or stereos. Be especially careful with headphones, which have the ability to generate extremely loud sounds, which may sound really great (until your hearing is damaged, anyway).