This story was originally published by Reasons to be Cheerful
7 min read
I spent years immersed in noise. Sometimes it was deafeningly loud, like the crescendo of horns and two-stroke motorcycles during rush hour in Mumbai. Other times it was simply maddening, like the parade of big-rig trucks in a dense Detroit neighborhood, belching fumes along with deep, chest-rattling rumbles and hydraulic wheezes. Some noises were jarring and distracting, while others — like the distant roar of highways and jets — kept intruding into the lush soundscape of the wilderness.
I not only listened to these noises, I studied them. I read about the serious health harms linked to this pervasive yet inscrutable pollutant, ranging from hearing loss to heart disease to childhood developmental delays. I wrote a book about everything I learned. But I still struggle to answer this basic question: What is noise?
The fact is that every definition misses some critical piece of the puzzle, and I have come to believe that characterizing noise too narrowly undersells its harms and hobbles solutions. The question of what separates sound from noise is worth exploring, but we should be open to multiple answers, all of which fall short but may collectively point us to a deeper understanding of noise and a better-sounding future.
Let’s start with decibels. Created by Bell Labs in the 1920s, the decibel scale measures a sound’s acoustic energy, which we perceive as loudness. For reference, leaves rustled by a gentle breeze might be 20 decibels (dB), normal conversation is about 60 dB, power tools generate about 90 dB, and a New York City police siren can hit 120 dB. For decades, this scale has been the go-to tool for most ordinances that regulate noise: Below a certain decibel level, it’s sound; cross the threshold, however, and it becomes “noise.”
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Defining noise by an objective measure such as decibels makes sense when it comes to the law. But in the wider world of noise, loudness is just one measure of sound, and not always the most important. Nature sounds, for instance, tend to lower stress levels, while the same decibel level of traffic sounds raises them, because our responses to sounds are anchored in memory and emotion. On a more basic level, studies find that people generally dislike “tonal” sounds with sustained high- or low-pitch energy like buzzes, hums and whistles, even relatively quiet ones.
The duration of a sound matters, too. Otherwise inoffensive sounds can become intolerable noise when they never shut up. This helps explain why the constant, low-pitched hum of data centers can drive people crazy even though the sounds are often well below the decibel thresholds of existing noise codes. Likewise, noise complaints to airports skyrocketed several years ago even though the jets weren’t any louder (in fact, they’d grown a lot quieter over the previous decades). Instead, the FAA’s new precision navigation system had consolidated flight paths, concentrating overflight noise disturbances.
