I think it wouldn’t have to be very loud, especially if the water is near the speakers. Sammyg said that the fields travel about five feet in the General Discussion thread:
I keep the volume at the regular volume that I would use for listening. A phone should be fine.
I find that wearing a tag and charging water with it each have slightly different effects, so I like to do both.
Charging water with a tag helps me accept the energy better, increasing the effects for me and dissolving some blockages, especially if the field is new to me. I also find it helps me assimilate the field better after using the Field Booster on a tag.
As our bodies are comprised mostly of water, perhaps drinking the water helps the field assimilate better by carrying the field to the water within our bodies.
It also helps to charge water when I’m trying to get the effects of more fields from tags but already wearing my personal maximum of five tags.