You really can't sound proof an average backyard chicken coop without creating some health risk. I've done a lot of research as a hobby lately on this very topic. You can however, add certain materials as insulation and figure out your noise direction. With this concept some of the noise will be dampened, some of it will escape and some of it will be redirected to another area that may not have a resounding echo effect you get with chicken noises. Roxul is expensive but can have multiple benefits as an insulator of sound and weather. It's more expensive, but very user friendly. Your standard R value batten insulation can also be effective. I have an Icelandic rooster and his crow is like a banshee. My parents next door really find it intrusive at points so I started doing a lot of research. I've managed using these tips to drop his voice decibels down several notches and take some of the piercing noise out if it. I do not believe nor condone the use of any kind of rooster 'collar' or any other device. There is noticeable difference in the sound now. You can still hear him, its just not as piercing and radiating as it was before.