I joke that the Slack notification has begun to visit me in dreams, but it’s unfortunately true. My days are punctuated by it, and now so are my nights. Each time I hear the sound ringing from my computer, it means that someone needs something from me: I forgot a task (slack), a deadline was moved (ping), god forbid someone is “circling back on the deliverable” over a public channel (slack). I breathe a little faster, muscles tense, navigating from one window on my tiny glowing box to another—life in the working world means life in the computer! I’m not the only one whose life has been transformed by Slack, millions in the knowledge economy abandoned the office in 2020—and probably all of us heard the change.

Although Slack may be the sound that’s brought work home, it’s not the only notification ringing in my head: there's also the clear iMessage bell, the warped gmail inbox tone, the scrambled twitter refresh, facebook messenger's insistent pop. Every platform has a unique notification, barring the personalized ringtones of the past—another trend that has signified a shift towards tech’s larger depersonalization, streamlined by an increasingly centralized, corporate internet—and all have started to build a world that is both immersive and interruptive, ripping your attention away from where your mind may drift otherwise. (ping) Welcome to the notification soundscape.

Most of the sounds that comprise these common notifications were engineered without scientific precision—just made to catch your attention like a musical hook would, combining contrast, sharp peaks and shifting scales. The developer of Apple’s now-famous tri-tone, Kelly Jacklin, dreamt it up in a day, and only after putting off the project for months. He generated a few samples, audio-engineered them with an algorithm, and then picked the catchiest one out from a lineup. He wanted a notification to be distinctive, signature and clarion, sharing his thought process in a 2013 blog post, “I was looking for something that would grab the user’s attention. I thought a simple sequence of notes, played with a clean-sounding instrument, would cut through the clutter of noise in a home or office.”

In another case, Slack’s founder Steward Butterfield sent his notification parameters to a musician friend, a sound engineer, who tinkered around on his drum kit for a day. Modeling it after jazz percussion, he recorded a loose rhythm, using a wire brush on a drum head and rapping his knuckles quickly three times in a row like an expedited door knock. Slack’s current in-house sound designer, Josh Mobley, described it as a swoosh-tap-tap-tap, calling it “Pavlovian,” “iconic,” and “very clever,” adding a little enviously, “I wish I’d made it.” In his interview, Butterfield seemed comparatively nonplussed by the knock-brush’s unique capacity to soundtrack millions of peoples’ workdays. Recounting the origins of the Slack “knock-brush” to an interviewer, he acknowledged the sound’s ubiquity and shrugged it off, “it’s Pavlovian, but I understand what it means; it has a significance and I’m not sick of it.” Okay, boss.

The “Pavlovian” aspect of the sound, like a dog beginning to salivate after hearing a dinner bell, is shorthand for a much more complex process of mental heuristics, exploited by the companies that best understand neuroscience and behavioral design. At a corporate level, marketers call this emerging space, venturing into sound, “sonic branding” or a “sound identity.” It’s shorthand for the explicit sounds we (consumers) have been taught to recognize for certain products. There are intrinsic sound effects, like the simulated rev of a Jaguar engine, the crunch of Kellogg’s cornflakes. And there are extrinsic sound designs like the iconic McDonalds jingle or the carefully engineered audio-haptic dynamic of an Apple iPhone. Extrinsic sound designs aren’t inherent to the fundamental mechanics of a product but we’ve been taught (via redundant, decades-long advertising campaigns) to associate the sounds with their product or experience.

These sounds are distinct from the music used in branding, which is composed to conjure a very specific, more imaginative concept of the possible, evoking feelings of nostalgia, happiness, allure and fear while pairing it with evocative visuals. Music is one of our most potent tools to amplify “consonant” emotions, intensifying experiences or drawing our attention away from them. There’s been considerable research devoted to the role of music in marketing and branding, acknowledging the ways we weave together emotional associations with s ub conscious thinking. Linguist Theo Van Leeuwen noted in a 1999 book that “although all sound stimuli may be considered from the perspective of common traits or dimensions, for example, amplitude, frequency, timbre, tempo, duration, texture, spatial location and reverberation, music is special.” The difference between an experience designed with and without sound, especially music, can be almost comical (think: TikTok videos on mute). Because music is so powerful—its psychological effect akin to a drug, and occasionally used explicitly as a medicine—some consider it ethically complicated to employ in a branding context. Researchers Nicolai Jørgensgaard Graakjær and Anders Bonde gave an insight into the complicated ethics of music in advertising, writing that “music in branding contexts has been fiercely criticized as a manifestation of instrumentally manipulated culture deployed in the service of social control.” In their piece, “Sonic branding and the aesthetic infrastructure of everyday consumption,” researchers Susie Khamis and Brent Keogh also “consider the ways in which sounds are embedded in contemporary brand practice and detail [how] popular musicians and genres are complicit partners in ‘branding to the senses’.”

But many brands have moved beyond music in marketing, developing shorter sonic identities as they might develop logos and other aspects of brand identity, designing them to permeate the explicit boundaries of advertising into the fabric of your life. In a meta-analysis, brand researchers acknowledged that attempts to cultivate extrinsic and intrinsic sound associations have been mostly successful; people recognize distinct sonic identities and the implications behind them. In response to this success, branding researchers have observed, and advocated for, a shift from the ‘visual turn’ to the ‘sonic turn’ as corporations aspire to keep up with a warier, but ever more immersed (read: online, captive) consumer base. In some cases, they’ve even developed methodological frameworks for better communication between multiple stakeholders designing sonic identities.

Predictably, those in charge don’t express ethical qualms with the use of sound in advertising or notifications. Serial entrepreneur Gary Vaynerchuk, who is sometimes called “the King of Digital Marketing,” and is revered in the startup space for his aggressive, bellicose delivery, declared that “Sonic branding will be the audio equivalent of a brand’s username.” There are already dozens of practical guides for designing “notifications that work” and designing sound identity in a corporate space. It makes sense that designers, marketers and product managers would be interested in these developments. When some estimates suggest we’re exposed to up to 10,000 ads a day, brand strategists are looking for any fresh entrypoint, including all 5 senses, to stake a claim on people’s crowded attention spans.

On the other hand, notifications are not explicitly intended to advertise—if they do, it’s with a distinctly more personalized and communicative intention. Notifications are semantic, carrying an individualized meaning and what researchers call “personally significant stimuli.” They divert our mental trajectories with “involuntary attentional distractions” not by introducing external incentives (like marketing would) but by reminding us of our existing connections, tethered to friends or work, or any of the seemingly ceaseless demands of modernity. A notification reminds you that there’s always something to do.

Just as words and tones have semantic implications, so too do the sounds that compose them. A wolf whistle is distinct from an ambulance siren, as a dog barking is distinct from a baby giggling—each invokes a differentiated neurological, and emotional, reaction. Mismatch Negativity tests measure an “index of sensory encoding,” letting researchers map which parts of the brain respond—and to what degree—to an “acontextual” sound. A recorded incidence of Mismatch Negativity (MMN) describes “an auditory event-related potential that occurs when a sequence of repetitive sounds is interrupted by an occasional ‘oddball’ sound that differs in frequency or duration.” Think of that oddball paradigm as your ringtone (a stimulus) blaring from your backpack at the library—your immediate impulse (response) is to start looking for your phone.

Because it’s a complex neural process to compute noise and instantly comprehend its meaning, humans have developed basic habitual heuristics to respond to oddball sounds. Psychology researcher Kaitlin Fitzgerald wrote that “a solution to the problem of complex processing in any limited system is the implementation of heuristics or short-cuts that serve to reduce and expedite processing.” The best example of these heuristics might be alarmist, things like cooking timers, fire alarms, or sirens that serve as easy pathways for diverting attention—if you hear a fire alarm, your brain knows immediately what to think. Our brain’s MMN processes are so effective that they’ve been termed pre-attentive, and are activated even without consciousness: people can respond to personally relevant or universally alarming sounds when they’re asleep, and sometimes when they’re comatose.

Every time our brain responds to a personally significant notification, our body receives a quick dose of cortisol, the same hormone that initiates the adrenal fight-or-flight stress response we know from encountering a threat. Dr. Sanam Hafeez notes that, “the alerts from phones or even the anticipation of them, shuts off the prefrontal cortex that regulates higher-level cognitive functions, and instead, forces the brain to send emergency signals to the body.” This heightened stress response is psychological, physical and emotional.

In the past decade, behavioral designers have exploited these psychological vulnerabilities, “hacking” our brain to cultivate cognitive reward sensitivities for our engagement. For example, a notification, once witnessed (whether heard, felt or seen), gives way to psychological phenomena like the Zeignarik Effect, which postulates that people will remember unfinished tasks more acutely than they’ll remember completed ones. The “nagging feeling” that arises when an activity is interrupted or incomplete, comes from our brain’s short-term memory impulses, urging us to finish one “micro-task” before starting another, but effectively disrupting both. In short, once you’ve heard a notification, it’s hard to forget it.

Behavioral designers have also aimed for other cognitive weaknesses. Phone notifications exploit our Restraint Bias and Attentional Bias by slowly eroding our already-overestimated willpower. Notifications that are engineered to be disruptive, visually or audibly, also take advantage of Salience Bias, a primary evolutionary mechanism that helps us identify patterns by noting what’s different. Think red dots on a white screen and morning alarms in a quiet room. Engaging with that notification makes us more likely to give those stimuli greater attention in the future, and in the short-term, lowers cognitive function and concentration.

The stimulus of a notification, the reason we’ve learned to pay attention to it—and what drives our impulse to attend to it, comes from either desire or fear (sometimes both?). The desire for pleasure is a fundamental part of the human brain’s motivational system—and the exhilarating rush of a new notification, of easy learning, and a quick chemical reward, means our body will pursue that pleasure without a regulatory impulse for the notification’s actual material outcome. Neuroscientists call this “Reward Prediction Error Encoding,” as an explanation for our response: the notification promises distraction, and the distraction promises a sweet hit of dopamine.

The other motivator, fear, initiates a different reaction—one that triggers a momentarily urgent response and residual, latent anxiety. A notification is a harbinger of stimulation, signaling the promise of either pleasure (as in the case of social media, texts, a push from your favorite youtuber) or fear (as in the case of work demands, slack, email). There’s reason to be wary of both, even as they infiltrate our soundscape with increasing ubiquity and what researchers call an “involuntary attention switch from personally significant stimuli” from ‘New Communication Technologies.’

What makes sound notifications so pervasive is that they’ve transcended the haptic boundaries of a phone or a computer, quite literally moving beyond a screen that you can touch and see to a sound that emanates beyond its boundaries. The notification is immersive because it expands our networked ecosystem. In his piece on “UX Design in the Age of Experience Ecosystems,” designer and theorist Marco Susani writes that “the environmental noise and the distractions of the environment balance this immersion, and provide meaningful context to our activity”—even when that activity is interrupted. An audible notification enables free movement through a system connected by our devices and our peripheral attention, uninhibited by a visual orientation towards the screen. By inserting itself into the soundscape, the notification becomes a part of the environment and the moment—and it will always call us back.

Unsurprisingly, this “excessive short term arousal/readiness is closely linked to longer-term wellbeing,” causing everything from phantom vibrations (experienced by a reported 89% of college students) to the permanent burnout that workers report almost 2 years into the pandemic—and as early as 2002 when Blackberries first made work accessible everywhere. We could turn notifications off, we could all live more quietly—if not in silence, merely in time uninterrupted by a constant stream of audible demands. But if my job’s on the line, or I instructed my friend to “text when you get home,” it’s hard to say no when the notification calls.

*slack sound* Back to work.