I believe that plants do respond to sound stimulus, lie talking to your plants and playing music aroung them. If noise helps in growth faster pace music is ideal. It would also make sense that the vibration from the soung waves would cause the plants to vibrate at high sound levels. I personally have a small stereo in a small grow closet going all the time. I only play metal, jazz, and clasical music to my plants. And even if it doesnt help the plants at all music's the best.