This is tough question with the information provided. Yes, you certainly can desensitize and counter condition the dog to startling sounds. You would need to determine if it is a startle reaction to sound only that she doesn't see happening. For example I can anticipate a loud noise if I see the chair falling. Another component, especially at an advanced age could be the dog's hearing. If she is losing her hearing, that could have an effect and I would have that checked first. I would continue to allow her to move away from any noises she finds scary or concerning. You could certainly reinforce the moving away (without any reactive barking, etc.) with a treat or toy. You would then need to determine the threshold for her sound tolerance. I usually begin working with recorded sounds so I can control the vlolume and duration based on the body language I observe. I would suggest starting with the hearing check and working with a experienced trainer or behavior consultant for the desensitization and counter conditioning as these take advanced skill to be effective. 

Desensitization / Counter-conditioning and fun training games White Noise Talk to your veterinarian

Counter conditioning is the best route along with trying to add some type of white noise, calming music (Through A Dog’s Ear) and Adaptil Collar or diffuser, a Wrap (like Thunder shirt) and discussing option with your veterinarian if the issue isn’t improving.

While using tasty treats / food to help a puppy’s reaction to thunder can be useful if done properly with a program that includes desensitization of thunder using a recording and counter conditioning other options can also help. Allowing the puppy or dog access to a space they feel safer like their crate or a room, etc. is fine. We all like to have a safe place, a sanctuary. I would also suggest continuing with the desensitization / counter conditioning, trying to add some type of white noise, calming music (Through A Dog’s Ear) and Adaptil Collar or diffuser, a Wrap (like Thundershirt) and discussing option with your veterinarian if the issue isn’t improving.

Yes, great start! I would reduce the volume as much as possible and watch the dog’s body language for signs of fear and anxiety. You could record the vacuum cleaner sound and counter condition the dog using the recording. I would try to avoid exposure to the sounds while you are working on this if at all possible.