Hello,
I’m sorry but there isn’t enough information here for me to offer much help. Please add more detail (how old is your cat, behaviors, vet care , medical issues,, etc?) and a description of the sound for more help.
In general this will require an examination by your vet to better understand the source and develop a treatment plan.
Is this a recent development? I would recommend a thundershirt, but be aware you need to put it on the dog BEFORE the storm hits. Medication can also help.
Beyond that, I would work on desensitization with sounds.
Additionally, I’d like to add my Doberman was not sound averse until after her spay, and she slowly increased in her storm aversion. She went from a dog who would stand outside and glare at the sky for daring to make noise when she was intact to a dog who’d cower on her bed post-spay. It was bizarre. We worked on desensitization training with Youtube videos and the highest value treats I had – bits of medium-rare steak. It helped.
Thanks for your response!! That is helpful. Yes it seems new and worse over the last year