Ah, feral dogs! They're like a whole different species, aren't they? You must be doing a great job with her; sounds like she's mostly stable. Those are hard dogs to raise, no question.
One of the things I've always found difficult with noise sensitivities is that it's so easy to make them worse when you're trying to make them better. I always take a Hippocratic approach: first, do no harm. Playing a desensitization CD by itself, without context, can turn a sensitivity into a phobia. So can improperly implemented counter-conditioning. If it's already getting worse over time, it won't get better on its own, so you have to get proactive.
It may seem like a roundabout approach, but having dealt with this a few times (personally and professionally), here's the strategy I've found works best for the most dogs:
1. Run through your basic obedience routine several times a day (at least 3) for about a week, so it becomes routine. We want Cricket thinking, "Okay, after the morning coffee, we do obedience...after mom (assuming gender...sorry) gets home from work, we do obedience...after dinner, we do obedience." And be sure she has fun, and gets this special one-on-one time with you. Vary the location and order of the tricks you ask for. Be excited, with lots of verbal praise and play time as rewards. Don't use a clicker and try not to clap when she does well. During fun training time, she'll already be aroused. Making sharp sounds at this time with an already sound-reactive dog will encourage her to associate those sounds with an aroused state, and we want to encourage the opposite. After each session, have at least five minutes of "cool-down" where you do whatever she'd like to do; play, snuggle, or take a walk. Anything works as long as it counts as "mommy and me" time.
2. After a week (ish), continue the routine, except between obedience and mommy-time, have a thick book ready. Show it to her, let her sniff it, then hold it at about her head height and several feet away from her where she can see exactly what you're doing. Drop it flat on the floor (carpet only--if there's no carpet, wrap the book in a towel first), then immediately put on a calm face and relax your body posture, and in a low, calm voice, say something like "Oh! Why did I do that silly thing? (Then excited voice
Wanna go for a walk?" (or whatever constitutes mommy-time.) If she barks, that's okay, but next time drop it from a lower height. (If she's still too upset, back up and start with a good, loud clap instead.) Keep smiling, and quickly move into mommy-time, like nothing ever happened. The whole thing, from picking up the book to resuming mommy-time, shouldn't take more than 20 seconds. We want it fast. We'll have her a little off-balance at this moment; hopefully her thought process will go, "Wow, what was that?! A walk, you say!" We want her to see that a) you aren't trying to hide the source of the sounds from her, b) your reaction to the sounds is "no big deal", and c) the sound isn't going to change squat when it comes to her fun time. We're using your relationship to communicate with and reward her. Follow this same routine for about a week as well. Before you make it more difficult, her reaction to this sound needs to be the same as yours: No big deal.
3. Now work it into the obedience routine. Go through the paces, then put her in a stay and do the book thing. Then quickly continue obedience, leaving the book wherever it fell, ignoring it completely. Behave like you don't even see it. She can look and sniff, but keep the obedience running like you normally would. Then mommy-time. Again, do this a few times (it may not take a week), until her reaction is calm.
4. Now you need a partner. While you're running through obedience, have them drop the book in another room, far away from where you're working. Pretend like you don't even hear it. If Cricket runs to investigate, the book is on the floor and your partner is going about his/her business, also as if nothing happened. No big deal. If she doesn't run to investigate, woohoo!! Complete obedience as usual, then mommy-time. Keep working on this step until she sticks with you throughout the routine. Then you can have your partner drop the book twice per session.
5. Now go back to step 2, except this time use a metal pot. She'll probably slip backward a bit, since this is a shift in the routine, but she'll get back to number 4 much quicker than with the book.
Continue introducing her to sounds by first showing her where they're coming from, and then having them come from another room. And the whole time, it's no big deal to you. As she gets better, you can work more sounds (stomping upstairs neighbors) into the routine. If at any time while you're working she runs off to bark at something noisy, just stay put. Don't call her back. Wait until she comes back to you, and ask if she's ready to continue. If not, be patient and don't react to the sounds, and especially don't react to HER reaction to the sounds. Don't tell her to be quiet, or try to redirect her. These are things that don't affect your day; let her see that, and follow your example. It may take about a month, depending on how reactive she is, but it's well worth it. Again, depending on how bad the problem is, we may be talking management rather than cure. But if we can stop a full-blown phobia developing, we've won the fight!