Today I told a parent, whose kid was squealing above the ambient volume of sound in the room: "if he gets excited, I can play with him outside, but we do need to keep the noise level down for our other customers."
The parent switched his dine-in order to takeaway, and left immediately afterwards. Our mutual friend later commented that the parent may have felt that no warning about quietness requirements had been provided beforehand.
My comments in subsequent discussions were as follows.
1. We're not a "quiet cafe," but we may tend to have lower ambient sound levels due to the nature of activities engaged in by many of our customers: studying, computing, reading. So when individual sound levels persist above the norm, we may raise the volume of music in order to raise the ambient sound level to a volume which makes it difficult for folks at adjacent tables to hear each other's activities. We may also remind individuals or groups to tone down out of consideration for their neighbours.
2. If an individual or group receives such reminders, they are under no compulsion to leave the premises unless explicitly directed by staff of the establishment. Following a reminder on communal disturbances, we expect individuals or groups to form their own judgments and to act accordingly. It is the staff's job to deliver announcements in the public interest.
3. We also happen to have a "keep quiet," sign stuck on the wall, in case extreme action is required to reduce sounds caused by any individual or group. It helps us to avoid the "no warnings were given," argument, but usually the guidelines on such signs are self-enforced by independent members of the public, and we do not refer to these signs explitly for more than 99% of the minutes of each shift.
4. Perhaps in Malaysia it is uncommon for folks to be informed when their group's audible volume exceeds the convenient threshold of ignorance for other groups. Therefore, this may cause a slight shock to groups who recieve such information. This is of limited concern to us - the appropriate behaviour for people in public is to be aware of their surroundings, and to constantly modify their interfaces with local environments as they move about the world. We are not responsible for norms caused by the failure of other establishments that do not remind their customers to be considerate of the general public within a space.
Ok, I should go to bed and stop working. :p