A couple years ago I had two roosters de-crowed. I live on a large property in an unincorporated suburb where my landlord is my neighbor. After my first couple clutches hatched & grew up I was given the edict that I could not have roosters because of the noise. So I sought a work around. The procedure was a success, performed by a specialized vet in Oklahoma. It cost me $175 a bird. I was very happy with the outcome. The birds were bearded Silkies. They had to be overnighted to the clinic in Oklaoma from California, then after the procedure & about a week of recuperation & observation, were overnighted back to me. I was very happy with the results. Unfortunately one of them caught some sort of respiratory infection shortly after coming home. The vet wanted 2k to put him on oxygen therapy & meds and I just couldn't afford it. I paid for the meds & took him home to nurse him as best I could, but he never improved & I lost him a few days later. The other "quiet roo" went on to a very happy life with his girls. His name was Lucky. He went through the motion of crowing but all that came out was a whispery whistling sound. It was kinda cute actually. He looked after the flock & all his girls loved him, they treated him no differently. He had no trouble doing everything a roo does, eating, drinking & mating.
The procedure itself involved making a slit in the larynx so that when the rooster goes to crow air can not be compressed over the vocal chords, it just escapes into the lungs.
For one season I had accomplished my goal. Sadly, all my efforts & investment were dashed later that fall with a mid-day coyote attack that took Lucky, one hen & two ducks