Why do loud noises scare cats and how do you stop annoying meowing?

Another thing I've noticed about my cat that Mom and I cannot seem to figure out is now my cat is afraid of outside city noises and I cannot figure out why city noises are now scaring my cat? Take for instance when certain noises like the garbage truck to the neighbors loud voices to car horns scare my cat my cat gets all freaked out and tries to bite and scratch and he will not calm down until the noises stop. Today when Mom was cooking dinner she was gently holding my cat when a horn sounded and he freaked out and scratched my mother. And Mom is so tired of getting bitten or scratched that she wants to put our cat somewhere else in the house when he freaks out. And this is weird because our cat was raised in the country and was used to these sounds
What can we do to ease his freaking out?

I think your cat must have experienced some kind of trauma involving loud noises, something you weren't there for. Either that, or they have ears that are twice as sensitive as normal cats. See, dogs and cats have hearing that's like turning up life's soundtrack really loud; so anything that's loud to you; it's nearly deafening to them, and it can be terrifying.

When our family got our first Rescue Dog, she apparently had developed a fear of loud noises before we got her, and was terrified of thunderstorms. Her first owner couldn't keep her anymore because he had gotten married and was moving into a new apartment with his wife that didn't allow large dogs. Aspen was an Alaskan Malamute; a large wolf-like dog that was bred for pulling sleds. Her first owner attempted to first give her away to ranchers out in the country, but he discovered what kind of heartless assholes they were when he came to visit a few weeks later. He was driving by a field on the way over, and found poor Aspen tied to a stake, with no food or water, with flies biting her ears, and starving. He had no idea how long she had been there, but he was horrified, and just untied her, took her back home, and nursed her back to health, never once speaking to the ranchers. We theorized that the ranchers had made the stupid assumption that Aspen was a herding dog, and when she couldn't be trained to do that, they got fed up and left her out to die in the field. Heartless SOB's. We also theorized that they had spanked her with fly-swatters, and that she had been out in a thunderstorm while staked in that field, because she was terrified of both.

Incidentally, all we could do was keep her in the house when she was feeling scared of thunderstorms or the air-cannon being fired at the college football stadium, and comfort her.

Perhaps your kitty needs someone to comfort them when they're scared.

Your cat needs it's own 'safe space ' . It could be a bed, or box or a cupboard. But somewhere it can go and be alone but feel safe.

Cats do not like change. They have their own territory and any disruption to this will put them on edge.

Make sure the safe space is a constant entity in your cats life. This way, they will know that there is always a safe place to be left alone.

My cat's space is under my bed. Any time I'm hoovering or there's a knock at the door, she will bolt under there. I don't pester her, she comes out when she is ready to.