Physical exercise is also a great bordom buster. Flirt poles and fetch are wonderful games to teach and play. Neighborhood walks are great a couple of times a week but play and training can give you more bang for your buck. Try these three games, for three days with three sessions of three minutes each. You will see the change, I guarentee it.
Noise Sensitivity Your dog could be jumping up and barking at "nothing" for a few different reasons. He could be scared of certain noises such as a garbage truck or your washing machine. He could associate sounds of the garage door opening with your arrival/departure.
Try to identify noises that your dog barks at and either use something like the Sound Proof Puppy App or simply get a recording on your phone or other device. You can turn it down very softly and reward your dog for calm behavior. Conuter conditioning will take place and your dog will become calmer
Barking at The door or guests If your dog is barking as guests arrive out of excitment you want to focus on teaching impulse control games. Games such as "Its Yer Choice" and "Zen Bowl" can have an incredible impact on their ability to control their excitment. Along side teaching alternative behaviors such as going to a mat or bed at the sound of the door bell.
If your dog is barking at guests out of fear then you will want to first work on greeting strangers outside the home. This is best done under the guidance of a qualified professional. Using classical conditioning you must work to change the underlying emotion and the behavior will change.
In contrast raising your voice or phyically correcting your dog's barking will not treat the cause. It might stop the unwanted barking in the moment which makes it seems like it is working. Barking is only a symptom, you need to determine the cause and from there decide how you want your dog to behave and teach them how.