It decreases by a factor of 1.4. It increases by a factor of 1.4. By blowing across the top of an empty soda bottle, a relatively loud sound can be created because a standing wave develops in the bottle. The speed of sound in the bottle has increased. The wavelength of the fundamental tone has decreased.
More overtones are present, hence the overall pitch of the sound is higher.
The speed of sound in water is higher than in air, so the sound wave travels faster in the bottle. There are nodes at each end of the tube. There are antinodes at each end of the tube and a node at the center. There is a node at one end and an antinode at the other. Trick question, air cannot vibrate in a tube that is open at both ends.