Sound waves with a large distance between a and b would be sound waves that have a large and produce loud sounds.

displacement of air  

Explanation:

Sound waves are mechanical waves that vibrate at a frequency of 20 to 20,000 hertz (Hz), and are normally perceptible by the human ear. Sound is the sensation we feel, through hearing through the action of this type of wave. Another important characteristic, the sound wave needs a medium to propagate, be it gas, liquid or solid. Therefore, there is no sound in a vacuum. The greater the air displacement produced by the sound wave, the louder the sound produced by it. For this reason, we can conclude that sound waves with a great distance between A and B would be sound waves with a large displacement of air and producing loud sounds.