a community of practitioners
Since you have has this discussion I would approach it this way. Get a coffee can and write on it that for those who break the sound barrier with loud talk or cell phones there will be a $1 charge. Contributed immediately into the can. This won't last long. No body likes to give up cash. If you do so in such a fun way (because we all may be guilty at some time) Come out and state you were loud and put the first $1 in while she is standing there.Then donate to an animal shelter or some other needed cause.
This is a very interesting subject. We can't all have ideal locations and noise is certainly a disturbance. As it was mentioned above the noise can come from those in the business, or it could come from the surrounding environment. In the case where 3 other people are using the place for business I am surprised this wasn't an on going problem. If all were working that would put 3 pairs of people having conversations or some clients talking on cell phones. I would have probably have had background music playing throughout if this was a problem. But many Therapists work in less than ideal locations. I would be more concerned about the lack of business and hope the new location proves better.
My place is next door to a restaurant. The kitchen wraps around our Therapy rooms. So we hear kitchen workers conversations, pots dropped into the metal sink and the scouring of the pots. I also have the benefit of music that is played in the dining room along one wall of one of the room's wall. As I am doing mostly therapeutic work for pain most clients don't really expect to relax. But they do. Those coming for relaxation usually fall asleep during the massage. Through touch we create a mood, an atmosphere. Perhaps it is not the outside noise that disturbs your client but your own annoyance conveyed through touch. I do not use music. I do this because I want all the focus to be on the clients body and what we both discover there as each area is massaged, soothed, relaxed. It surprises even me how suddenly there can be loud snoring over the sound of banging pots as the massage advances.
We do not live in a perfect world we need to work within the environment and create an atmosphere. This comes first from your touch and then from anything else you choose to create.