Would love to speak up about this... no pun intended
As owner of LouVino, which has already received a reputation of being extremely loud, here is my take... which echos (again, non pun intended) what others have already said.
1) Design - the focus on our design, as well as many others these days, is industrial. Wood, metal, hard surfaces. None of which absorb sound. Carpet? No way in a restaurant... you would go out of business cleaning it. Curtains? No thanks... would remind me of my grandmother's house
What's "in" for design doesn't help for better acoustics... just the way it is.
2) Sound absorption - we recently had sound engineers in to give us a bid to make our space a little more quiet. Their bid came back at $11,000 and when asked if/how much it would help they essentially said "maybe" and "we won't know until we do it".... SO, there isn't a magic equation to come up with exactly what to do, how much to do, etc... like many may think (so many people have commented to us and said "just put some acoustic panels up" -- easier said that done!!) It's all a guessing game and unfortunately, it's an expensive one. I will also add that this quote was to put fabric panels over almost every inch of wall/ceiling. So, instead of a neat, clean look... it would look like we are an art gallery of fabric panels...
Furthermore, in the highlands we are dealing with building that are built like tanks which again adds to the acoustical nightmare.
3) Drinking - the more people drink, the louder people get. Can't do much about that.
4) Popular places - All of the restaurants that were mentioned in this post are extremely popular, packed places on most nights (ours included). Sorry, but packed places are going to be loud... probably no matter what you do. Restaurants are a low margin business and we have to do what we can to maximize those Fridays and Saturday nights to stay in business in order to keep Louisville a great foodie town. Even "fine dining" places like Jack Fry's are loud on busy nights.
5) Some people actually like it - we have had people of all ages say that they love our atmosphere.
6) We want it loud? I can guarantee you that we aren't going for this... we want a nice mixture of a lively atmosphere with good conversations. Some might want that... but it leads to negative comments about your restaurant which doesn't bode well for business.
Just my 2 cents, from someone who is currently dealing with the issue with no great solution, even by the experts.