I would say that volume of the music affects the ears of humans and animals, not the plants' growth. Below is the text written by one of our scientists in reference to a question related to the one above.

The major things plants require to grow are light, nutrients (usually the get nutrients through soil), water, and carbon dioxide (the gas that is released when organisms breathe and part of what is release through fossil fuel burning - like from driving cars). Plants may seem to grow better when you play music for them, but that is likely a side effect of being better tended because people might notice more often when they need to be watered, fertilized, and generally taken care of more often.