grating
Harsh and annoying to hear, like a scratchy sound.
Grating describes a sound that's harsh, irritating, and unpleasant to hear. A grating voice might be high-pitched and whiny, or it might scrape and rasp like nails on a chalkboard. When metal scrapes against concrete, it makes a grating noise that makes you want to cover your ears.
The word comes from grate, which means to scrape or rub roughly. When you grate cheese, the cheese scrapes against the metal holes with that distinctive scratching sound. That uncomfortable, scratchy quality is exactly what makes sounds grating.
A person's laugh, voice, or way of speaking can also be described as grating if it's annoying in a persistent way. If your classmate has a grating habit of tapping their pencil constantly during silent reading, the repetitive sound wears on your nerves. The word captures both the harsh quality of the sound and the way it affects you: it doesn't just sound bad, it actively bothers you.
Grating can also be a noun: a framework of parallel or crossed bars, like the metal grating that covers a storm drain in the street.