To determine which option would not increase the velocity of a sound wave in air, let's analyze each choice based on the principles of sound propagation.
A) Lowering the humidity of the air - Lower humidity means more dry air, which has a higher density than humid air. Sound travels faster in humid air compared to dry air. Thus, lowering humidity would likely decrease the velocity of sound.
B) Lowering the density of the air - Sound travels faster in less dense mediums. Lowering the density of air would increase the velocity of sound.
C) Increasing the wind speed in the direction the wave is traveling - The presence of wind can affect the perceived speed of sound relative to a stationary observer. Wind can help carry sound waves faster in the direction it is blowing, effectively increasing the speed of sound relative to an observer.
D) Increasing the temperature of the air - Sound velocity increases with temperature due to increased kinetic energy of the air molecules.
Based on this analysis, A) Lowering the humidity of the air is the option that would not increase the velocity of a sound wave in air. In fact, it would likely decrease it.