Americans don't value silence the way other cultures do (I'm an American btw). I'm not sure if it has to do with the ratio of introverts to extroverts, or if it's simply that we're an individualistic culture, but often I strain to hear in a restaurant these days. Anecdotally, I've noticed that the higher end restaurants tend to be quieter. Not sure if this is because of clientele or the higher quality construction of such places blocking more sound.
While I was in Japan, I noticed that it was quite possible (and many did) to take a nap in McDonald's. Conversations indoors tended to be very reserved.
As a country, I think we're getting louder. I've brought a Decibel Meter with me before and seen it hit north of 70dB. This constant level of noise everywhere we go can't be good for our hearing.
It doesn't take much sound dampening to significantly lower the sound in a public place, due to the positive feedback loop. Take a restaurant with tile floors and cheap ceilings -- not only does that make it louder, but people have to then talk louder to be heard. And that in turn makes the volume even louder yet. And table cloths really make a big difference also.
Another thing that can affect volume is the density of tables in a restaurant -- same feedback loop in place. If you can't hear the conversation at the table next to you, then you can speak in a lower voice also.
Some of that is intentional. I've heard lore about people eating faster and getting out sooner if the restaurant is louder.
Also heard lore about casinos using extremely bright and dizzying carpet designs to get you to avert your eyes from the floor, and onto the gambling equipment.
"the carpets are deliberately designed to obscure and camouflage gambling chips that have fallen onto the floor. The casinos sweep up a huge number of these every night. So the carpets are just another source of revenue."
Would there be money in machine vision to recognize fixed-layout outliers on regular patterns (i.e., fallen chips on the carpet) and scouring casino floors for a night?
I can definitely believe there is some truth to the casino carpet one. Las Vegas carpets are the only thing that has ever made me suspect I might have photosensitive epilepsy. I don't, but those carpets more than anything else in that city give me crippling headaches.
Touristing through Texas, I visited the Caverns of Sonora. You're taken through the caverns in a group, and at the nadir the guide turns the lights off so you can hear what it's like in the dark cavern. My otherwise-quiet tour group (all Americans bar me) went absolutely nuts with the chatter when the lights went off. It seemed less about 'talk to alleviate nervousness' and more 'teacher's not watching, let's yammer!'. Lights went on and the chatter reduced again. It was very, very weird.
Higher-end places in America do design their spaces to be somewhat smaller, intimate, and mute sound. Diners and management also respect auditory space a little more when you're spending big bucks on a meal.
These places also don't blast rock music over PA systems while people are trying to eat. I've been in some joints where it's literally an arms war between the diners and whoever has their hand on the volume control. Management wants the place to seem lively and hip, but by the end of the evening people are literally shouting themselves hoarse.
Playing music louder and dimming the lights to reduce visibility is a technique used to make a place seem busier than it actually is.
I once visited a restaurant that appeared to be using this technique when we were the only people in the entire place (~7500 square foot space). I literally had to lean across the table to shout at a coworker because he couldn't hear what I was saying otherwise.
What you seek in restaurants I look for in bars. Those with a more mature crowd lack the obnoxiously loud club music* of college bars. Often these bars have a broader selection as well, though you pay for it in dollars.
In the summer, I spent a few weeks in Taiwan. The quietude and calmness even in a group setting made it a lot easier to focus on a group engineering project. Mostly though, I miss the food.
While I was in Japan, I noticed that it was quite possible (and many did) to take a nap in McDonald's. Conversations indoors tended to be very reserved.
As a country, I think we're getting louder. I've brought a Decibel Meter with me before and seen it hit north of 70dB. This constant level of noise everywhere we go can't be good for our hearing.