Also, many new visitors mistake the Loop for downtown, but the Loop is really just one part of downtown. Downtown encompasses River North, West Loop and a bunch of adjacent neighborhoods where it's fairly lively. Parts of the Loop can be pretty lively at night too, especially off State St where the theaters are (I just saw Hello Dolly last night).
I mention this because there are many midwestern cities (like St Louis) whose downtowns are completely deserted after 5 which gives rise to safety concerns. Chicago's downtown isn't like that at all. It's still comparatively residential. It's somewhat similar to downtown Toronto in that the core business district clears out after 7 and the surrounding areas become more lively.
Architecture and urbanism generate pedestrian activity, and many midwestern towns are not designed for it, but for people to come from the suburbs and park near their office. You can use zoning to build lively neighborhoods, soulless collections of office buildings, or anything else in between. The many municipalities around St Louis, and their planning, also engineer world-leading levels of segregation, both by race and social class. It's no wonder St Louisians ask each other where they went to high school. The way the metro area is designed, it'd be a miracle if it didn't provide a lot of information.
Hotels often put earplugs on the nightstand since it’s so loud in some parts.
Related to honking and street noise, another factor I noticed is a high number of curbs where parking is simply not allowed. This streamlines traffic in some ways, as people aren't fighting over spaces or waiting for someone to back in slowly. Although, there was a lot of "hazard parking" where people just stopped where they weren't supposed to. A lot of the honking I witnessed was due to freight/waste vehicles blocking an entire street (2-4 lanes) so they could back into a dock or service area in the middle of a block.
Downtown at night seemed eerily quiet, although there were a good number of people. I think several factors applied here, when compared with SF... Chicago has been built to handle the vast crowds from events and conventions that swarm the city. When that isn't happening, there is comparatively more room for people, so it's wide sidewalks aren't as crowded. Also, being built to withstand harsh winters, I imagine there is better thermal insulation that also acts as decent audio insulation (plus a lot is happening under the street level!). I was right outside blues and jazz clubs where you couldn't actually hear that anything was going on inside (this makes me laugh when compared to visiting Nashville for the first time earlier in the year).
It also seemed that the contention between drivers, cyclists, and pedestrians is more severe even than SF, where I saw several interactions that seemed more like a macho game of "chicken".