Here are some options from one of our trainers, but you may want to talk to a professional trainer.
2. Get into the habit of involving the dog in something else reinforcing (e.g. play, Kong) after a PT session so they're being consistently rewarded for a non-barking behavior in a situation where they habitually bark and develop the habit of disengaging from the PT.
3. Shape a quiet settle with the PT, gradually extending the amount of time the dog can be around the PT without barking.
4. If the dog barks after the session, visibly and conspicuously remove the PT machine from the dog's sight at that point. The function of the barking is likely to be demand/solicitation. Training them that barking actually makes the whole machine disappear would be pretty potent -P for my dogs (and therefore not a first tier option for me)
5. Extinction, which would not be my go-to for most dogs but is an option. Leave PT available and let the dog bark until they realize it's not reinforcing.
Downsides of extinction: frustration, escalation, lots of noise to wait through, and barking can be self-reinforcing.