Honestly, Sylvia is rather quiet. Not much noise to be heard unless she’s pushed to bark. She doesn’t bark when people knock on the door or pass by the house, she watches or listens but I also spent some time just teaching her not to make noise. Bourbon is still a puppy and makes a lot of noise that I would just categorize as normal puppy noise, like throwing fits and crying but outside of those events she’s also pretty quiet. Depends on the individual and training in my experience
Packs of dogs (not just borzoi) are known to just break out into a pack howl though and I do know borzoi where alarms/sirens is enough to get them to howl but it’s few and far between.