New York City is almost never without noise. It is the city that never sleeps. Even if you live high up like I do, there's white noise from all the rooftop machinery that buildings use. I have a fabulous terrace that I rarely use. These days, the city often sounds like a war zone: the sirens are endless as are the ubiquitous helicopters.
I'm spoiled because the interior of my apartment is unusually quiet for a city center apartment with an expansive view. When friends and guests visit, they inevitably say something like, "It's so quiet here, I'd never know I was in NYC." Now that I'm older, I so appreciate the quiet quality.
I've always considered myself a light sleeper, so decibel levels at night really matter to me if my goal is solid, uninterrupted sleep. Those of us who live in big, noisy cities tend to be immune to the sounds of big-city nightlife. The younger you are, the more immune one can be. If you're a first-time visitor from a rural location in the U.S., the sound of Rome at night can devastate.
I will never forget my first night attempting to sleep in Rome. I was a young guest in a clergy community just around the corner from the Trevi Fountain. My dark, bathroom-less room, one flight above the ground floor, had one window, and it faced a narrow vicolo (small alleyway). At 12:30 AM, in a jet-lagged stupor, I shockingly discovered how popular that vicolo was with Vespa owners seeking a shortcut. I didn't sleep well at all that debut evening. The echoed sound of roaring motorcycles bouncing off stone buildings shook my bed frame as if I was experiencing an earthquake while listening to an Imax version of Transformers.
A smart traveler who cares about quality sleep in Rome will eventually learn to pack earplugs. But they won't be just any earplugs, since most of the stuff that's easy to get your hands on does not qualify for suppressing high decibels. For places like Vespa-ridden Rome, you need silicone earplugs, the kind that rock-n-roll sound engineers use when they're on the road with Metallica.
If you're the type of traveler who likes to over plan, a good night's sleep is crucial to a successful trip. Without good sleep, your energy level, your stamina, your attention span, and your memory will suffer.