You blow across the open mouth of an empty test tube and produce the fundamental standing wave of the air column inside the test tube. the speed of sound in air is 344 m/s and the test tube acts as a stopped pipe. if the length of the air column in the test tube is 15.0 cm , what is the frequency of this standing wave? what is the frequency of the fundamental standing wave in the air column if the test tube is half-filled with water?