When Oliver barks unnecessarily, I give a sharp "AAAH!" and pop his leash. This usually distracts him into stopping the barking and looking up at me. I tell him "don't worry about that" in a nonchalant way and continue on our walk. He will also yelp at me when he wants up, especially on a new walk, and I do the same thing. He knows that the "AAH!" noise means he is doing something I don't like.
I also have been training him to "Speak" since he was 2 months old. This can be very useful and may be worth a shot for you, since it helps control his noise level. Once you've taught him to speak, you can teach him 'quiet'. I am working on this now and it's fairly successful.
When your dog is barking, try clapping your hands loudly and saying "Quiet!". If your dog stops, praise and reward. I use dehydrated beef liver as a treat and Oliver loooooves it. He will do almost anything for it. Practice a lot. you can even encourage your dog to bark, such as during play, and use that time to practice the "quiet" command.
This article is great. I taught 'speak' before 'quiet' because he wasn't barky enough for me to teach quiet first.
Speak / Quiet Commands - How to Train Your Dog to Speak or Be Quiet
Good luck! I know how ANNOYING a yappy dog can be so I feel for you.