Why do cats make weird noises when their back is scratched?

Answer 1

Not all felines will exhibit a licking behavior when their back is being scratched.

The licking behavior, while common, is more of an individualistic behavior, and most likely a grooming response. When the cats back is being scratched, the cat feels something similar to self grooming or grooming from another cat, and some will lick the air in time with the stroking.

Licking in response to stroking or scratching is not necessarily a species wide behavior however, and not all cats will react similarly.

A response that is very close to being species wide is the movement when the base of their tail is scratched. Most cats will stiffen the legs and tail, raising their posterior high on straightened legs and many will additionally appear to point their lower jaw, stiffen the neck and turn their head toward their back. Most experts suggest that cats enjoy having the base of their tail scratched... 1.) Because it is sexually stimulating, and 2.) because this is an area inhabited by fleas and scratching there relieves an itch. I suspect that both may be factual.

It is not advisable to attempt this scratching on a cat you are not very familiar with, as some will be inclined to bite when the base of their tail is scratched; especially if the scratching is done a bit too aggressively.

Answer 2

A cat could be making weird noises when the back is being scratched because it does not like it. Another reason could be because the cat does like it. The personality of the cat depends on the reason the cat is making the weird noise.

Answer 3

because it has no way of scratching it really good on its own