Here's the scenario: I'm in a restaurant enjoying lunch with a friend. We're having an in-depth conversation about something important. However, we keep needing to ask each other to repeat what we've said because the occupants of the table next to us are talking very, very loudly. This is a prime example of grown-ups forgetting to use "inside voices." It's a problem I'm noticing at an alarming rate!
The DH believes part of the problem is due to the constant sensory bombardment in our society. He thinks that folks are so often "plugged in" that they forget what it's like to have quiet conversation. Reference points become talking over an iPod, rather than over a table in a public setting. It's a plausible theory.
In terms of proper etiquette, your conversation in a restaurant should reach the ears of your table partners, but not beyond. Even though you're in a public setting, your conversation should be private. The same philosophy goes with cell phone use. Please, do not subject me to your latest boyfriend breakup or plans for the weekend. If you need to make a cell phone call, the best option is to find a private location and keep your voice down. In restaurants, cell phones should be off or on vibrate. If you have to make a call, step into the lobby or, even better, outside. And please, keep your voice down!