Can you control volume on digital piano?
So, yes, it is possible to control the volume of any digital piano. Since the sound is generated through electronics, and not through the actual physical process of vibrating piano strings, then the ONLY way to hear the piano is through amplification.
How loud are digital pianos?
I think you'll find it's really hard to get a digital piano into the ear-damage range of 90+ decibels. If you're using an external sound system, you could get past 90+ decibels, but that's why it's good to have a sound meter, so you can be sure.