Isleep on the second floor, in a bedroom facing a residential street in Brooklyn. Through the years, my sleeping brain has grown used to the nighttime noises of motor vehicles: mainly the growls of engines, but also the squeaks of truck springs wheezing over the street’s speed hump, and the wheedling of open-door chimes from late-night Uber drop-offs.

Fire engines, cop cars, unmuffled Harley-Davidson motorcycles, not to mention unhappy couples arguing and the occasional lost soul screaming at ghosts—none of that noise bothers me. On my first night in the country, however, I’m like Joe Pesci in “My Cousin Vinny,” trying to sleep in rural Alabama: “What the fuck is that?”

Unlike vision, smell, and taste, all of which dim when consciousness shuts down for the night, hearing is a 24/7 operation. For early humans, who were trying to rest outdoors with predators around, this trait was presumably a lifesaver. For people trying to sleep in the city that never does, though, all-night listening is mostly a liability. The brain must disregard a lot of ordinary metropolitan white noise, while remaining alert to unusual sounds that might be of vital importance. The waking brain performs a similar filtering function in the urban soundscape, ignoring as many of the meaningless noises as possible.

Researchers into the neurobiology of hearing explain this phenomenon in terms of novelty and adaptation. Familiar and regularly patterned sounds, such as internal-combustion engines and air-conditioners, don’t wake us; a new or irregular disturbance stands out, at least at first, amid the sonic clutter. In a 2005 paper, Ellen Covey, a psychologist at the University of Washington, and her co-authors identified these subconscious arbiters of sound and noise as the brain’s “novelty detector neurons.”

But a novel or useful alert can become a meaningless repetitive noise over time. The beeping emitted by the new Walk / Don’t Walk signals, which were recently installed on the corners of my block, initially struck me as abrasive; now I tune it out. Other, more aggressive sounds, such as back-up beepers on trucks, have been designed to resist assimilation, because that would diminish their efficacy as audible beacons. Far from blending together into a kind of acoustic ecosystem, city noises tend to compete with one another to be heard—an auditory cage match wherein the loudest sound eventually wins.

The electrification of mobility presents humanity with a rare opportunity to reimagine the way cities might sound. Electric motorcycles, cars, trucks, and vans are legally mandated to replace all internal-combustion-engine (I.C.E.) vehicles in New York, L.A., and other cities by mid-century—a shift that will profoundly alter the acoustic texture of urban life. The internal-combustion engine, in addition to being the single largest source of CO₂ emissions, is the leading cause of global noise pollution, which studies have shown to have a similarly corrosive effect on human health. When moving at higher speeds, electric vehicles, or E.V.s, produce roughly the same wind and road noise that I.C.E. vehicles do, but at lower speeds they operate in near-silence: electricity flows from the battery to the motor, which spins with a barely audible hum. Therein lie the promise and the peril of E.V.s for city dwellers.

A zero-emissions vehicle has obvious benefits for the environment, but a quiet car is a mixed blessing for the public good. Automobile engines, however annoying non-driving citizens find them, are rich in information, providing a protective web of sound that cushions us from collisions as we navigate the streets. Not only does engine noise announce a vehicle’s presence; it can also convey its direction, its speed, and whether it is accelerating or decelerating. The same disturbances that my brain ignores while I’m sleeping help guide me when I’m cycling in traffic and can’t take my eyes off the road to glance back. And, for pedestrians distracted by their phones, engine sounds are everyday lifesavers, as the tiger’s distant roar was for napping early humans. Except that the predators are motor vehicles—and the new ones are virtually silent.

In response to this threat, Congress passed the 2010 Pedestrian Safety Enhancement Act, a law that few Americans paid attention to at the time, and that took almost ten years to implement. As a result of the legislation, every E.V. and hybrid manufactured since 2020 and sold in the U.S. must come equipped with a pedestrian-warning system, also known as an acoustic vehicle alerting system (avas), which emits noises from external speakers when the car is travelling below eighteen and a half miles per hour. (Similar regulations apply in Europe and Asia.)

Automakers have enlisted musicians and composers to assist in crafting pleasing and proprietary alert systems, as well as in-cabin chimes and tones. Hans Zimmer, the film composer, was involved in scoring branded sounds for BMW’s Vision M Next car. The Volkswagen ID.3’s sound was created by Leslie Mándoki, a German-Hungarian prog-rock/jazz-adjacent producer. The Atlanta-based electronic musician Richard Devine was brought in to help in making the Jaguar I-Pace’s voltaic purr. Some automakers cooked up sounds entirely in-house. The Porsche Taycan Turbo S has one of the boldest alerts: you’re in Dr. Frankenstein’s lab as he flips the switch to animate the monster. Engineers in the Audi Sound Lab made the lower frequencies of the Audi E-Tron GT Quattro’s alert by algorithmically mixing different tones produced by recording an electric fan through a long metal pipe; the full alert references the sumptuous soundscapes of the film “Tron” and its sequel.

Other alerts tilt more toward nature. Danni Venne, the head designer behind the Nissan Leaf’s Canto sound palette, said in a Business Insider video that “you really have to go for instruments that don’t have a hard attack to them. Wind instruments, flutes, oboes, clarinets . . . can kind of waver a bit.” Elon Musk has suggested that Teslas could make goat noises, or, perhaps, clopping-coconut sounds, like those made by the crusaders in “Monty Python and the Holy Grail” because they lack actual steeds.

Only one in twenty new cars sold in the U.S. is an E.V., so these alerts are still a rarity in New York, but one day everyone will live with them. I’m already wondering how I’m going to sleep.

It took a lot of effort to make naturally quiet vehicles noisier. The campaign that led to the Pedestrian Safety Enhancement Act began at the grassroots level. One November morning in 2003, a friend dropped by the Illinois home of Deborah Kent Stein, a blind writer and an activist with the National Federation of the Blind, or N.F.B. The friend wanted to show Stein and her family his new Toyota Prius, a hybrid vehicle. “It’s completely silent when it’s running on its battery,” he announced. “No kidding—you can’t hear a thing.”

Stein later described this fateful encounter with the automotive future in an essay she published on the N.F.B.’s Web site:

I stood at the curb and listened as our friend climbed into the driver’s seat and slammed the door. I waited to hear the Prius hum into life and move forward. I heard the chatter of sparrows; the distant roar of a leaf blower; and, after a minute or two, the opening of the car door.

“When are you going to start?” I asked.

“I did start,” our friend answered. “I drove down to the end of the block, and then I backed past you and drove up in front of you again.” I felt a cold sense of dread. I thought, we’ve got a real problem.

A few years later, Lawrence D. Rosenblum, a professor of psychology at the University of California, Riverside, read something about the danger of quiet cars. He had done acoustic research showing that the brain pays special attention to sounds moving toward the listener, automatically calculating what Rosenblum calls “time-to-arrival.” He published an account of his work in a 2010 book, “See What I’m Saying: The Extraordinary Powers of Our Five Senses.”

With a grant from the N.F.B., Rosenblum set up an experiment in which blindfolded subjects stood next to a roadway and listened as both a gas-powered Honda Civic and a hybrid Prius running on its battery drove past. Subjects were told to press buttons on a device to indicate when they could hear a vehicle and to identify its direction. The results, Rosenblum told me, “couldn’t have been clearer. People could hear the Honda when it was still twenty feet away, whereas they couldn’t hear the Prius until it had passed them.”

At its headquarters, in Baltimore, the N.F.B. established a committee to investigate the problem of quiet cars. Discussions were held with automotive regulators and auto-industry engineers. “Smart” solutions were proposed involving sensors, cameras, and in-cabin alerts that would warn an E.V.’s driver of an impending collision. The sonic plague of back-up beepers unleashed by Ed Peterson’s mid-sixties invention, the Bac-A-Larm, has been tempered by back-up cameras in newer trucks and vans, which warn only the driver, and not the rest of the street, if someone is behind the vehicle. Couldn’t E.V. alert systems work similarly, especially with the proliferation of sensors and cameras in the latest models? But the blind community strongly opposed that approach, in part because it was predicated on an imminent collision, rather than on preventing such incidents from occurring in the first place.

At one meeting, an automotive engineer made a suggestion. Since maximum-noise laws for gas-powered automobiles already existed, why not establish a minimum-noise standard that E.V.s had to meet? “It was a revolutionary idea,” Stein wrote.

But, in order to convince Congress to consider a law requiring a minimum-noise standard, the N.F.B. needed data. And in the nineties and early two-thousands, with so few hybrids and E.V.s on the road, the number of accidents involving pedestrians, visually impaired or not, was statistically negligible. The N.F.B. did collect many anecdotal reports about close calls, and even accounts of minor injuries. “But anecdotal evidence isn’t statistical engineering evidence,” John Paré, the N.F.B.’s executive director for advocacy and policy, who served as the national coördinator of the campaign against quiet cars, told me.

Without real-world data proving that quiet cars could be dangerous, the National Highway Traffic Safety Administration, the federal agency charged with reducing deaths, injuries, and economic losses on the nation’s roadways, could do nothing. The breakthrough came later in the decade, when the N.H.T.S.A. investigated crash rates for hybrids and E.V.s in incidents involving sighted pedestrians and cyclists, and compared those with crash rates for I.C.E. vehicles in similar incidents. The results, which were published in a 2009 report, based on limited data from 2000 to 2007, showed that hybrids and E.V.s were twice as likely as I.C.E. vehicles to be involved in accidents with pedestrians. A follow-up report in October, 2011, using a larger sample size, found that hybrids and E.V.s had a thirty-five per cent greater likelihood of accidents with pedestrians, and a fifty per cent greater likelihood of accidents with cyclists. Most of these incidents occurred not on the road but in parking lots and driveways, when a driver was reversing or turning.

The Pedestrian Safety Enhancement Act, calling for a “sound or set of sounds for all vehicles of the same make and model,” was passed in the last hours of the 111th Congress, and President Barack Obama signed it into law on January 4, 2011. The Act did not specify what those alerts should sound like. That question took six years for the N.H.T.S.A. to resolve, and resulted in three hundred and seventy-two pages of mostly numerical acoustic rules and parameters. What took so long?

“We thought that they had to sound to some degree like cars—otherwise, the alerts won’t provide safety,” Paré told me. “Society has already been trained to know what cars sound like.” However, he added, “it’s really hard to specify what a car sounds like. How do you put into regulatory legal language that a car should sound like a car?”

Many electrical appliances make sounds, although few are scored by famous composers. My family’s seven-piece kitchen ensemble, for example—dishwasher, electric oven, microwave, refrigerator and freezer, electric kettle, and coffee maker—creates a discordant symphony of simple beeps, tones, and chimes of clashing frequencies and rhythms throughout the day to inform us when the machines have begun or completed the particular tasks they were designed for. An acoustic ecosystem it’s not.

Electric vehicles offer a vast new stage for sound designers, both inside and outside the vehicles. As sensors, computer vision, and cloud-based algorithms take over more and more of the driving, sound will become a user’s primary interface with such machines. If a car can drive, its user won’t need to look up from her book or wake from a nap unless there’s an audible alert. Many newer cars, outfitted with semi-autonomous features that assist a driver in adjusting the speed or changing lanes, already make in-cabin sounds when they perform these actions, mainly to reassure the driver and any passengers that the vehicle is executing a plan, and not just randomly drifting. (In psychoacoustic research, these are known as “priming” sounds.) There are also more urgent collision-avoidance alerts, should a car’s cameras or sensors detect objects close by.

Nicolas Misdariis is the head of the Sound Perception and Design group at the Institute for Research and Coordination in Acoustics/Music (ircam), in Paris, a world center of psychoacoustic research. Since 2008, his team has worked with the Renault Group, designing sounds for the French automaker’s lineup of electric cars, both prototypes and vehicles in production.

ircam’s office is next to the Pompidou Center, in Paris’s Fourth Arrondissement, and as I walked there one day in February to visit Misdariis I kept mostly to the streets, because the narrow sidewalks were overflowing with pedestrians and electric-scooter riders. I listened to the whine of diesel-fuelled cars and the whokada-whokada of two-stroke mopeds behind me—engines that give European cities a different audible flavor from American urban environments—in order to know when to get out of the way. The only close calls I had were with the shareable e-bikes that Paris, like New York, has embraced since the pandemic. E-bikes are not legally required to emit sounds when moving—yet—although some proactively do.

When the researchers first began working with Renault, Misdariis told me, the collaborators struggled to find a common language in which to talk about acoustic design. “When a graphic designer says to you, ‘This is a red triangle,’ there is no different interpretation possible,” he said. “But if you say, ‘I would like a warm sound’—what is a warm sound? What is a round sound? What is a rough sound? A green sound? What is a smiling sound? We know what happy music is, but what is a two-second sound that is happy?” Misdariis added, “It is the sound designer’s job to translate high-level visual representations into sound parameters—this is a very tricky point of our discipline.” The Renault team eventually developed tools for visually sketching sounds, frequencies, and modulations. “We needed these tools to create efficient sound design,” he said.

The ircam researchers also investigated fundamental issues such as whether E.V. sounds should be sonic metaphors for the noise of internal combustion, similar to a cell phone’s synthetic bell or the reassuring paper-crumpling that indicates you’ve discarded a document on your MacBook—a form of acoustic design known as skeuomorphism. Another option was to use “ear-cons”—audible symbols, such as the abstract clicks a Geiger counter makes, which everyone recognizes as the sign of radioactivity. Misdariis’s team developed and tested options in both categories. They discovered, he said, that “metaphors are easy to understand but hard to remember, whereas symbols are harder to understand but easier to imprint.”

The ircam team worked with Andrea Cera, an Italian music producer and composer. Cera said that he views the electrification of mobility as a chance to fundamentally rethink the chaotic acoustics of a city. He envisions an urban soundscape modelled on birdsong in nature, in which, instead of competing to be heard, different sounds fit into an over-all acoustic ecosystem. By analyzing soundscapes around the world, Cera told me, he has identified “these little niches where you could put a little sound so that you could be present without being loud. Just a tone, not a melody.” The sounds he and the ircam team have designed for Renault aim to complement those niches. He added, “If the soundscape is very chaotic—cars, phones, horns, radios—the best way to be noticed is to be still.”

ircam’s Renault sounds were, indeed, surprisingly mellow, although perhaps less like birdsong than like a washing machine set to the delicates cycle. The Parisian soundscape will surely benefit from them. But would anyone hear these élégantes French alerts in New York, particularly over the bedlam and blare of all the gas-powered vehicles in its traffic-clogged streets?

An automobile powered by internal combustion makes a racket. The induction of air, its compression inside the piston sleeves, the explosion of the vaporized gasoline, and the expulsion of CO₂ exhaust (“suck, squeeze, bang, and blow,” in car talk) produce loud, low-frequency reports, rumbles, and vibrations.

At General Motors, engineers in the Noise and Vibration Center are responsible for fine-tuning that din. Douglas Moore, a senior expert in exterior noise at G.M., started working at the company in 1984, when he was still an undergraduate at Michigan State. He has spent all but eight years of his career with G.M., where his job, and that of his Noise and Vibration colleagues, has been to silence, dampen, and modulate the sounds made by internal combustion, depending on the brand. Traditionally, when tuning a Cadillac, Moore and his colleagues would try to make the engine as quiet as possible, because quiet signifies luxury to the classic Cadillac buyer. In tuning a Corvette, Chevrolet’s “muscle car,” on the other hand, the engineers want some of the bang-bang-bang of internal combustion to come through, because that conveys power to the driver.

The engine’s sound isn’t the only thing that the engineers work on. Many prospective buyers’ first experience of a car or a truck is the CLICK ker-CHUNK that the driver’s-side door makes when they close it, followed by a faint harmonic shiver given off by the vehicle’s metal skin. The door’s weight, latches, and seals are carefully calibrated to create a psychoacoustic experience that conveys comfort, safety, and manufacturing expertise.

In designing electric versions of popular brands, U.S. automakers have to decide whether to make the E.V.s mimic their gas-driven counterparts or whether, like Renault, to divert from the familiar sound. The Passenger Safety Enhancement Act directives allow automakers to craft their own branded alerts, so long as they meet certain specifications.

Moore’s first E.V. project was the 2012 Chevy Volt, which emitted a pedestrian alert years before the law required one—a vacuum-cleaner-like hum that increased in frequency as the car sped up. “I have new colors to paint with,” Moore said. “Instead of a palette of internal-combustion sounds, I have a palette of avas sounds. But it’s the same approach. Now, instead of generating them with the physical components of the car, which has its pros and cons, we’re generating them electronically.”

Moore is also the longtime chair of a group within the Society of Automotive Engineers called the Light Vehicle Exterior Sound Level Standards Committee, which helps develop tests that regulators use to measure safety on the road in the U.S. His group led the investigation into developing minimum-sound standards for E.V.s and hybrids, and establishing parameters to govern the decibel level, pitch, and morphology of the warning signals. Moore once came to the N.F.B. headquarters and tried navigating in traffic when blindfolded. His N.F.B. instructor was impressed that the engineer could identify a 2005 Chevrolet Camaro and a 2009 Cadillac Escalade by their distinctive engine sounds.

Moore explained the S.A.E.’s relationship with federal highway-safety regulators by saying, “We figure out how to measure things. N.H.T.S.A. says how much.” I asked Moore why the regulations don’t require that E.V.s more closely resemble I.C.E. vehicles, since, as the N.F.B.’s John Paré had noted to me, we’re already used to those noises. Moore replied, “The purpose of this sound is to provide information about what the vehicle is doing. And there’s more than one way to provide that.” He paused. “Yes, we’ve learned internal-combustion sounds over a hundred years,” he continued. “But before cars were around we knew that the clip-clop of horses meant the wagon was coming. So, there’s nothing inherent in those engine sounds.”

A well-designed alert reaches the people who need to hear it, without annoying those who don’t. To thread this sonic needle, engineers can vary a particular sound’s decibel level, which indicates the volume of air pressure that the sound waves displace, and they can also adjust the sound’s pitch, or frequency. Both decibel level and pitch determine the intrusiveness of that sound. The danger is that you create a sound that cries wolf, as it were: it works at first, but after a while people tune it out, so you have to pump up the volume.

Although humans are capable of hearing frequencies between twenty and twenty thousand hertz, we hear in “octave bands,” in which the highest frequency is double the lowest one. (In a musical C octave, the high C is twice the frequency of the low C.) The regulations specify that avas sounds must cover four separate, nonadjacent octave bands. A so-called broadband sound of this type, such as the staticky squawk that Amazon delivery vans recently began making when reversing, is less piercing, more robust, and easier for the hearer to locate directionally than an alert that occupies a narrow frequency range, such as the back-up beepers on Con Ed trucks. Not incidentally, the nonadjacent-octave-band rule precludes using a musical phrase as an alert—the pitch-shifting would sound awful—as well as any vocal alerts, human or animal. How would the blind tell the street from the sidewalk if electric cars spoke or barked?

By permitting automakers the latitude to brand their alerts, the N.H.T.S.A. rules have created a new design form: acoustic automobile styling. Pedestrians and cyclists won’t just hear the vehicle coming; they’ll know what kind of car it is. For acoustic designers, both the pedestrian alerts of E.V.s and their rich in-cabin menus of sonic information represent the dawn of a new age. “I feel fortunate that I get to work on features that will influence the way the world will sound,” Jigar Kapadia, the creative-sound director for General Motors, told me.

Kapadia, who studied electronics and telecommunications engineering at Mumbai University and has a master’s in music technology from N.Y.U., collaborates with Moore and others at G.M.’s sound lab in Milford, Michigan. For each sound, the team comes up with about two hundred variations and then tests them on their colleagues in the jury room, until they have arrived at a few finalists they can road test on vehicles.

Kapadia likens an alert-system sound to a perfume. “Just like a perfume, it unfolds,” he told me. “The alert has a base note, a middle note, and a top note.” He added, “These layers are amalgamated together to bring out a cohesive organic sound, or a futuristic sound, based on what kind of brand we are focussing on.” He noted that the pedestrian alert on the 2023 Cadillac Lyriq, the first electric version of G.M.’s long-standing luxury car, was made with a didgeridoo, an ancient Australian wind instrument that is based on the musical interval known as a perfect fifth. However, for G.M.’s nine-thousand-pound electric Hummer, which recently went on sale, Kapadia said, “we wanted a more distorted sound.” He paused, and then added, “A bold Hummer sound.” The Hummer’s forward-motion alert made me think of church, when the organist launches into the next hymn. The back-up sound is something like its dystopian twin.

At the Ford Motor Company, in order to find out what car buyers thought electric vehicles should sound like, engineers and consultants conducted “customer clinics” and launched a Facebook campaign. Judging from the number of responses, Ford fans were keen to make their opinions known. My own survey, largely based on reading comments under YouTube videos of various branded E.V. sounds, is that most people think that E.V.s should not resemble I.C.E. cars. Higher frequencies are thought to signify clean energy and software-driven intelligence; E.V.s ought to whoosh and zoom like the flying personal vehicles of science-fiction films such as “The Fifth Element,” “Gattaca,” “Blade Runner,” and, of course, “Star Wars.” In many cases, in fact, Foley artists created those futuristic vehicles’ sound effects from recorded I.C.E. noise. In Ridley Scott’s “Blade Runner 2049,” the twist is that Ryan Gosling’s flying vehicle sounds like a broken-down I.C.E. jalopy.

Ford’s Brian Schabel, a sound engineer who, like Moore at G.M., has spent his career in Noise and Vibration, was part of the group that worked on the Mustang Mach E, Ford’s sporty but practical electric S.U.V. “We knew we wanted to keep some aspect of that low-frequency modulation and link it to the past,” he told me. “And then we looked at everything out there. Machinery—what do people associate powerful electric motors with? Formula E vehicles are very high-pitched, raw-sounding. How can we blend those two pieces together? We didn’t want something that was too ‘Batman’ or ‘Blade Runner.’ ” Mach E’s forward sound put me in mind of a hovering dragonfly. The back-up sound is like a broadband cricket.

In creating the company’s new palette, Ford collaborated with Listen, an audio-branding firm based in Brooklyn. One member of the Listen agency, Connor Moore (no relation to Douglas), is the founder of CMoore Sound, and has worked with Google on Firefly, its self-driving-car project, as well as with Tesla, Lucid, Uber, and other tech companies. An electronic musician, Moore explained that he uses the same process and production tools for cars that he relies on to make music, mixing synthetic tracks with recordings of physical objects and nature sounds.

“With the F-150 Lightning,” Moore said, discussing the electric model of Ford’s immensely popular pickup, “you’re thinking about the size and the scale of the car. So some of that means recording heavy objects: metals, stone, things that have weight. You want something with low-end distortion that hits you in the chest. We also worked with more organic elements, like wind and water sounds, and clay and wood. We really leaned on a lot of the organic material for the in-car alerts.”

I asked Moore about the possibility that, by allowing for a unique identity for each of the sixty major auto brands in the world, we were setting ourselves up for a sonic catastrophe—a cacophony of competing thrums and whirs and chimes and tones. If every car is emitting a unique branded alert as it passes under my bedroom window, aren’t my novelty detectors going to go haywire? I described my street to Moore, noting that there is a traffic light about twenty yards away, where there are often six or eight cars waiting. Once the cars are all E.V.s, will I need to move to an apartment at the top of the nearby ninety-three-story Brooklyn Tower just to get some sleep?

Moore replied, “I think with intentional-design thinking we can actually, maybe, make the world quieter. That’s my goal.” However, he added, “we could wake up in five years with eighty per cent E.V.s, and it’s a cacophony of sound and dissonance if these cars are all singing different tunes, in different key signatures and pitches.” Moore speculated that cities might one day have to designate a particular key for all the alerts made in their streets. (I nominate F-sharp major, the key of Jay-Z and Alicia Keys’s “Empire State of Mind.”) On second thought, Moore said, “maybe, you know, that would potentially drive people crazy.”

Then there is the question of how customizable a vehicle’s alert system should be. In 2017, automakers petitioned the N.H.T.S.A. to be allowed to offer drivers a range of options that they could select from. The agency, after a public-review period, denied the request for safety reasons, but the issue could come up again. If Boombox, a software feature in Teslas, is any indication of what’s on the way, it will be difficult to limit the sounds that drivers play through E.V.s’ external speakers. Boombox, which was released in December, 2020, as part of a software update, allows Tesla drivers, according to its promotional literature, to “delight pedestrians with a variety of sounds from your vehicle’s external speaker,” including goat bleats, ice-cream-truck music, applause, and flatulence. In early 2022, the N.H.T.S.A. found the Boombox feature noncompliant with its rules. Musk called regulators the “fun police,” but Tesla nonetheless issued a firmware update that prohibits the use of Boombox when driving, although hackers will probably find a way around it. Teslas can still fart when parked.

Another possibility is that New York City is just too loud for the relatively civilized decibel levels established for the alert systems by N.H.T.S.A. regulations. Douglas Moore told me that “the levels are set to where a normal person would be able to hear it in a normal situation. It is not expected to be heard in all places”—such as construction zones—“at all times. Otherwise, you’re in the death spiral of just cranking the levels up.”

But a death spiral could be what we get. Because, after all, what’s the point of an alert if you can’t hear it? I borrowed a Mach E not long ago, and took it for a spin around Brooklyn with a colleague who was planning to record the car in motion. He jumped out on Kent Street, in Williamsburg, and stood with his microphone as I drove past, but the Mach E’s forward-motion alert barely registered. As a second-story sleeper, I was reassured. As a cyclist, not so much.

Just before six the other morning, while I was still asleep, my hearing picked up a novel sound coming toward me: a thud-thUD-THUD, reverberating off the façade of the apartment building across the street, getting louder as it came closer.

Was it an E.V. alert? I woke up just long enough to grasp that it was someone bouncing a ball down the middle of the street. After passing under my window, the THUD-THud-thud faded until the street was quiet again. At 6:45 a.m., the first of the garbage trucks came by.