Guns go bang. It is difficult to find a quiet one that has not been modified. It depends on what you need. You can easily kill a coyote with a 22 lr, the quietest option.You can easily hit it to 100 yards. Recover the carcass at night, not as easy. Same for an even quieter option, a crossbow. But coyote would run off and you would lose your bolt.
The best option by far, suppressor. But expensive and long wait.
Those are the legal options.