Engines can develop some unpleasant noises under certain conditions, thanks to fiendishly complicated harmonics in the intake-air tract, and so clever engineers often use the principles of Helmholz resonance to devise hardware to reduce drones, moos, blatts, and honks. Most of these devices look like little plastic boxes growing off intake-air ducting, but the anti-honk boxes— "honk box" being my preferred term for this stuff— in my hooptie 1992 Honda Civic hatchback are the most elaborate I have seen yet.
Here we see the anti-honk box in a 2013 Scion FR-S. It's a simple rectangular plastic box, attached to the intake-air system via a dignified little tube.
In the 1992-1995 Honda Civic with D15B7 engine, most of the anti-honk gear is hidden, with just a little snout next to the air cleaner as the tip of the iceberg. The rest of the hardware hides in the area to the front of the passenger-side fenderwell and down into the space behind the bumper. I had no idea it was there, until I was forced to remove all of it to make room for the 1996 Acura Integra GS-R air-intake bits that I am swapping into my Civic in an ill-advised engine-transplant project.
I can't begin to guess how much it cost Honda to equip each Civic with such serious dehonkification components, but the honk problem must have been serious to make adding even a few bucks to the cost of each car necessary. The 1992 Civic DX listed at $9,850, cheaper than even the least expensive Chevy Cavalier, and this was just in time for the bursting of the Japanese asset price bubble. I can't fit all of the Integra dehonkification gear in my Civic, so I'll need to run a Cherry Bomb muffler to drown out the honk.