Does turning the volume up make the vibrations more intense?

You can control the resonance created by the SO SoundHearts and the volume of the speakers individually.
Please do know that sometimes “less is more”. In other words, while you may not be as aware or perceive all frequencies being delivered at first, you are still getting the benefit.
As you use the SO Sound system more and more, you will notice that your level of kinesthetic perception increases. This is because as we “exercise” our brain and body/mind into more balanced states, we release muscular tension and stress which is what inhibits our ability to feel and we expand our consciousness awareness.