When I kept green tree frogs as a kid i ran into the same problem occasionally but I had 4 males and 4 females. When kept really wet they would go into breeding mode and males would call a lot at night.....and they are loud! My parents were so upset with me! I had to move their enclosure to another room. They subsequently laid 2-300 eggs. Keeping them on the slightly drier side might reduce their activity and the males calling behavior. Sometimes they call in response to sounds like the radio/tv/laundry machine/dogs ect. Fortunately you have one male so it will probably be easier than 4 males which egg one another on.