Area 7 has a single building on the upper right. Stand in the middle of the building and press "up", you can enter a hidden communication room. Communication will tell you to knock on the right wall 5 ...

Capcom is in real danger of shooting itself in the foot here. As well as its big-budget re-imagining of Bionic Commando, it is also releasing Bionic Commando Rearmed as a cheaply-priced download.