The Noise You Don’t Hear

Soundscapes that vanish by design

This may be obvious to anyone who has ever gone to sleep, but for me it took hours of observing my baby to draw the unscientific conclusion that the amount of noise a person can slumber through depends on the amount present when falling asleep. If you pass out in the presence of road construction, then the scraping of steel on asphalt will blend right into your dreams; but drift off in the cottony quiet of your bedroom and even the slightest rattle of a window pane may jolt you awake.

Luckily, there is the magical sound-neutralizing antidote of white noise. When I put my kid to sleep in his crib, there is a secondary, sonic crib surrounding him, protecting his dreaming mind from erratic door slams and garbage disposals. A defunct iPhone from our household graveyard of obsolete devices generates non-stop shushing via an app called “Asleep,” represented appropriately with an icon of a sheep.

Back in the day (and still, if you are a purist), such a designer soundscape would have been produced by an actual white noise machine — perhaps purchased at Brookstone or from the Skymall catalog — the sole function of which was to project specialized static for peaceful rest, productive work, or distraction from tinnitus. In the book Making Noise, Hillel Schwartz beautifully describes the advent of white noise machines:

Out of [the research of psychologists, engineers, otologists, and psychophysicists] during the Second World War came machines that did nothing but make noise, once the technical province of children, toy companies, siren designers, fireworks firms, shamans, and claques. The noise of the new machines had to meet newly rigorous specifications: it had to be noise at any decibel level, to any ear, through any volume of space, at any time. It would be noise because, by definition, it was random and carried no information; it could be heard only as itself. “White noise,” this would be called, by inaccurate analogy to the optical white noise that is all spectra of light…White noise is patternless sound, “featureless and unpredictable at all frequencies,” rather than an olla of all sounds.

This was a bit revelatory to read, because I’ve been convinced many times, while sitting in the dark awaiting the steady, shallow breaths of a sleeping baby, that I could pick out component parts of what I always assumed was a melange of familiar sounds — what I’d probably have dubbed brown noise for all its indistinguishable messiness. I’m sure I can hear the honking of horns, the ringing of bells, random voices, water dripping. Apparently, like hallucinating in a sensory deprivation tank, the aural blur generates illusions.

App stores carry scores of on-demand soundscapes. The first one I tried featured pages of options: birds, oscillating fan, wind, ticking clock, urban rain, heavy rain, rain on roof, monk chant, cat purring, and one called “afternoon.” Another enabled custom sound-mixing, so you could mash up a campfire, a metronome, and a galloping horse.

We call all of these things “white noise,” but technically, none of them qualify. As Schwartz points out in the excerpt above, true white noise is by definition patternless, random and non-repeating, while the sounds available on the app are simulations or recordings of recognizable noises. And that’s a problem.

Because like hearing your own name called out in a busy coffee shop, recognizable sounds trigger listening. They cut through the din. And all we want from white noise is not to hear it. In a sense, it is the opposite of music. It should be designed to disappear before our very ears, an audio elephant in the room.

White has a very precise scientific meaning,” explains Stephane Pigeon, an electrical engineer and sound designer based in Brussels, “When it comes to a spectrum, it means that all frequencies are present, in equal proportion. It is indeed an analogy with light, which turns white as soon as you mix all the frequencies (colors) together in equal proportion. So, a signal (e.g., sound) that has all the frequencies present — from 0Hz to infinity — with the same levels, is described as white.”

What’s interesting, however, is that while all frequencies playing at equal levels gives us the purest version of this randomized noise, most human ears find it too harsh. Instead, we favor “pink noise” (really, that’s what it’s called), which deemphasizes the higher frequencies and hews closer to sounds found in nature.

Not being a sound geek myself, I was unaware until digging into this story that the sound spectrum is classified like the light spectrum along a spread of rainbow colors, with the lowest frequency being red and the highest violet. So not only can you have white noise and pink noise, but also blue, grey, brown, and so on.

Pigeon, who is a sound geek, believes that “we are still living in the ice-age of noise machines,” stuck with non-adjustable white noise generators when we could be custom-designing the color of our noise to perfectly fit our needs — “a noise whose ‘color’ compensates for your personal hearing thresholds, the flaws of the speakers or headphones you are using, and takes into account the characteristics of the sound you want to mask.”

At Pigeon’s personal website,, to which he dedicates most of his time outside of his day job, the dream of custom-colored noise can be realized. He has built a noise generator with ten slider bars that you can manipulate yourself until you reach your own optimal static — the kind that “after a while, disappears from your conscious perception.”

Now, whether or not we need this level of personalization is debatable. In most human environments — and especially in cities — there are already ambient noises that act as fairly consistent “white noise” generators. Seth Horowitz, a neuroscientist and author of the book The Universal Sense: How Hearing Shapes the Mind, explains urban infrastructure as one giant sound machine.

“Sound travels faster through denser materials so in a typical city with lots of streets, the roads of the entire city are acting like a giant low-fidelity speaker and creating these noise bands,” he explains, adding, “It’s also why Venice is so quiet even though there’s thousands of people — no roads.”

Buildings, too, can be designed to produce noise that masks various sounds arising from activity within. As Hillel Schwartz points out in his book, the crescendo in office noise resulting from typewriters and telephones, then computer keyboards and conference calls, demanded a sonic envelope that could dull the aural sensitivity of the workers:

Architects who used double-paned windows, sound-absorbent panels, and acoustic ceilings to cope with the noise of typewriters and ringing phones in the open-plan offices that arose during the 1950s would by the 1970s use heating and ventilation ducts to add in white noise as “sound curtains” veiling desktop clicking and as “acoustic perfume” to give officeworkers a shared backdrop of productive, communal activity.

In 2005, these strategies were taken to the power of computing when the renowned supercomputer architect Danny Hillis and industrial designer Bran Ferren of Applied Minds brought to market a new invention called Babble, which was intended as a substitute for walls and acoustic tiling in offices. The clock radio-sized device, as described by John Markoff in The New York Times, was “composed of a sound processor and several speakers that multiply and scramble voices that come within its range,” effectively making phone conversations private without putting up physical barriers. Design giant Herman Miller brought the device to market, with dreams of extending the breadth of their office offerings beyond furniture like the beloved Aeron Chair.

The Babble didn’t take off, for reasons unknown (at least by this author), and Herman Miller’s acoustic tech subsidiary, Sonare, seems to have faded away, as well. Perhaps because all most people need, whether working or sleeping, is a pair of ear buds with a looping little sound clip of ocean waves. The loop itself might even be meditative, if you’re not the kind of person who’s driven batty by repetition.

“One of the great nuances in fine hip-hop production is that the seam within a loop becomes a conscious sonic element, the moment appreciated for its textural quality, its role as a beat,” reflects Marc Weidenbaum, who since 1996 has explored the role of sound in the media landscape at the website But there again, we have the problem of creating sound that’s intended for focused listening, versus designing a sonic environment that evades attention. If a loop draws notice, the white noise isn’t doing its job.

“Theoretically speaking,” says Weidenbaum, “somewhere in between a live generation of noises and the rudimentary employment of loops might be a system in which multiple loops of varying length are employed, and each loop cancels out the other loops’ seams.”

What you need if you’re going to generate noise that does not loop at all is computer processing power. “A good study point here is video game audio,” explains composer and sound designer Robert Thomas, “Game designers face the same problem as the [white noise] app manufacturers. They have a limited space to store sound files and don’t want their users to hear repetition.”

Thomas outlines three workarounds. Let’s take my waterfall track as an example:

1. (most simple)Use a long compressed file format loop of a waterfall which is sonically flat and doesn’t have too many recognizable elements which would highlight looping. Also ensure that loop points are unrecognizable using zero crossing loop points and fading the end of the loop into the start. This is not great from a game designer’s point of view because it expands the size of the game / app a lot. But it can result in a reasonable quality sound.
2. (more complex) Use granular playback of a sound file of a waterfall. Granular playback plays many small chunks or grains of sound from a file in a randomized or unpredictable way to create variance or control of the sound. This can recombine many of these grain fragments from the original waterfall to create a stream of sound which is constantly slightly different. There is no loop point as such.
3. (most advanced) Don’t use a waterfall recording at all. Instead, synthesize the sound effect procedurally. This means creating a convincing mathematical model of the sound of a waterfall and running that with randomized parameters — creating the sound instant by instant — just like the real waterfall does with water, air and physics.

Thomas recommends that sound designers use a combination of the three, and relies on the increasingly great computing power of our ever-smaller devices. Weidenbaum, on the other hand, attributes the success of various noise mostly to our fallible brains. “Me, I think culture plays a big role in these matters. I think some people respond better to expensive white noise machines because of the incredibly complicated human experience of spending money, the weird reflexive psychological factors involved.”

Lucky for us, then, I suppose, that Stephane Pigeon’s bespoke noise generator is a free service offered to all who visit his website or download his app. He has a pay-it-forward attitude about applying his engineering skills to help people relax, focus, and sleep better.

But Pigeon has a meta goal beyond simply designing the perfect noise. He wants to design new language for talking about sound, one that abandons the use of color names as a stand-in for audio frequencies. “The colors are one of the very first things that your baby will learn,” he tells me. “One of the first books he will receive will be the one with those colorful figurines and the names of each color printed in bold letters: blue, red, green. As he grows up, he will learn myriad color names, and will be able to distinguish them, very precisely: this is not blue, exactly, but turquoise, or cyan, or indigo…”

Not so with sound, he laments. “The vocabulary doesn’t exist yet. Something that has no words associated with it has no chance to exist culturally.” Until we invent a new lexicon dedicated to sound (not to music, which he concedes we have, but to sound itself), we are left with the colors of the rainbow. And for most of us without deep knowledge of this field, we don’t even have that. It’s all just a lot of white noise.

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Cover photo by Andrew Malone on Flickr