You can always talk it out with your husband. If you can't express it to them in the face, try to communicate through their son. But just make sure that you will explain it clearly and carefully so you will not be misunderstood.
I have the same problem, but in my case, I live with my family. Sometimes, my baby is already sleeping but still, they're not sensitive enough to keep it down low. But at the end of the day, I'll just let it slip. After all, we're a family. :)