I am as curious as you are because I've been wanting to get a service dog as well for all kinds of things including this but I don't find any information much on what it can do for adults with autism.

You totally can if you can get a provider who is willing to write you a letter confirming the plan and need for a service dog. You just need a documented diagnosis and the dog needs to have two jobs it’s trained to do to help with the symptoms. For example, in your scenario one job might be to ground you by nudging you when you begin to dissociate. Another might be licking your hand when the noise in the space you’re in rises to a certain level to give you an external signal that you may become overstimulated, at which time you can check in with yourself and take a break outside or move to a different location. The letter may also need to say that you’re experiencing significant impairment due to these things, so you might mention to the provider if you’re doing things like avoiding leaving your house because of worrying about this, or if you frequently have panic attacks or end up in potentially dangerous situations when you do go out and end up overstimulated and dissociating. For example, if you tend to have times when you’ve driven or walked home in a dissociated state where you don’t remember the journey. Then after you’re able to get a letter and create a plan for the two jobs the dog will have you begin the training phase. During this time you can consider your dog a “service dog in training” and they should have all the same rights as a fully trained service dog. The training includes teaching them your specific two tasks as well as “canine good citizen” behavior, which you can google but basically consists of doggie manners in public and ensuring that they have practice staying in tune with you even in distracting situations so they can continue to do the jobs you teach them even with those distractions. It’s also important to note that you have the right to train your dog yourself, and that you’re not required to spend thousands of dollars on dog training. You can of course hire someone if you need help but you have the right to do it yourself if you can’t afford hitting someone or if you just prefer it that way. Another super important factor is finding the right dog for the job. Not every dog has the personality and temperament for every service dog job. For what you’re talking about specifically it would be important that even before training the dog is pretty comfortable around people and with sounds. Yes dogs can learn and be trained but it’ll be easier on you and the pup if you start with one who’s a bit of a natural in those settings rather than for example one who gets spooked by people or tends to bark at every little unexpected sound. Hope this is helpful and that you can find a provider willing to support you through this!