Well, no, the speed of light in all inertial frames is defined to be the same, not measured. But the speed of sound can be measured in any situation, it doesn't have to be defined in order to make a meaningful Frame of Reference.
No, there are no sealed environments that cause light to behave differently than it would in an unsealed environment. And this shows a difference between light and sound. In order to get sound to travel at the same speed in a moving environment (like an airplane) as it would outside on the ground with no wind blowing, you have to seal the air inside from the air outside so the air inside will seem like it is stationary with respect to the airplane. With light, you don't have to do that. Even out in the open, as long as the airplane, or spaceship, or whatever, is traveling at a constant velocity (and we are ignoring the effects of gravity), it will appear to have exactly the same characteristics as any other similar situation.