A glass tube open at the top is partially filled with water, creating an air column of length \(L\) that is open at the top and closed at the bottom by the water surface. A tuning fork held near the top of the tube vibrates, generating a standing wave in the air column at its fundamental frequency \(f\). Water is then drained from the tube until the length of the air column increases to \(2L\). What is the new fundamental frequency of the air column?