I wont say it cant be done, but I think you would run a greater risk of ruining the dog than breaking it.
not being smart, but If your wanting silent then why buy the dog? If its catching hogs regularly then I wouldn't worry bout the yipping.
My dogs r silent, but she would be a good addition to my pack but im afraid of her making my dogs open. But yes you may be right if i want silent i may jus need to pass her up and find a silent dog of her quality.