What should a nine thousand pound electric vehicle look like?
IRCAMRenault’s sounds were, indeed, surprisingly gentle, though perhaps less like birdsong than a washing machine set to the delicate cycle. The Paris soundscape will surely benefit. But would anyone hear these elegant French alerts to New York, especially about the hustle and bustle of all the gas-powered vehicles on its congested streets?
An automobile powered by internal combustion makes noise. The induction of air, its compression inside the piston liners, the explosion of vaporized gasoline and the expulsion of CO2 the exhaust (“suck, squeeze, thump, and puff,” in car parlance) produce loud, low-frequency gears, rumbles, and vibrations.
At General Motors, engineers from the Noise and Vibration Center are responsible for fine-tuning this din. Douglas Moore, GM’s senior exterior noise expert, started working for the company in 1984 while still a student at Michigan State. He spent nearly eight years of his career at GM, where his job, and that of his noise and vibration colleagues, was to silence, attenuate and modulate the sounds emitted by internal combustion, according to the brand. Traditionally, when tuning a Cadillac, Moore and his colleagues tried to make the engine as quiet as possible, because quietness equates to luxury for the classic Cadillac buyer. In tuning a Corvette, Chevrolet’s “muscle car,” engineers want some of the bang-bang-bang of internal combustion to pass through, as this transmits power to the driver.
Engine sound isn’t the only thing the engineers are working on. The first experience of many potential buyers of a car or truck is the CLICK on ker-CHUNK what the driver’s side door does when you close it, followed by a slight harmonic shudder emitted by the metal skin of the vehicle. The door’s weight, latches, and seals are carefully calibrated to create a psychoacoustic experience that conveys comfort, security, and craftsmanship.
When designing electric versions of popular brands, US automakers must decide whether to make electric vehicles mimic their gas-powered counterparts or, like Renault, to deviate from the familiar sound. The Passenger Safety Enhancement Act guidelines allow automakers to create their own brand alerts, as long as they meet certain specifications.
Moore’s first electric vehicle project was the 2012 Chevy Volt, which issued a pedestrian alert years before the law mandated one – a vacuum-like hum that increased in frequency as the car was accelerating. “I have new colors to paint with,” Moore said. “Instead of a palette of internal combustion sounds, I have a palette of AVA 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 generate 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 USA. His group led the investigation into the development of minimum noise standards for electric and hybrid vehicles, and the establishment of parameters to govern the decibel level, pitch and morphology of warning signals. Moore once came to NFB headquarters and tried to navigate traffic while blindfolded. His ONF 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 SAE’s relationship with federal traffic safety regulators, saying, “We figure out how to measure things. NHTSA says how much. I asked Moore why the regulations didn’t require electric vehicles to sound more like ICE vehicles, since, as John Paré of the NFB had pointed out to me, we’re already used to those noises. Moore replied, “The purpose of that sound is to provide information about what the vehicle is doing. And there’s more than one way to deliver that. He stopped himself. “Yes, we learned internal combustion sounds in a hundred years,” he continued. “But before the carriages were there, we knew the clip-clop of the horses meant the carriage 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 the decibel level of a particular sound, which indicates the amount of air pressure the sound waves are moving, and they can also adjust the pitch or frequency of the sound. The decibel level and pitch determine how intrusive that sound is. The danger is that you create a sound that sort of cries wolf: it works at first, but after a while people turn off, so you have to turn up the volume.
Although humans are able to hear frequencies between twenty and twenty thousand hertz, we hear in “octave bands”, in which the highest frequency is twice the lowest. (In a musical octave in C, high C is twice the frequency of low C.) The rules state that AVA the sounds must span four distinct, non-adjacent octave bands. A so-called broadband sound of this type, such as the static screech that Amazon delivery vans have recently begun to emit when backing up, is less shrill, more robust, and easier for the listener to localize directionally. than an alert that occupies a narrow frequency range, like the backup beeps on Con Ed trucks. Not coincidentally, the non-adjacent octave band rule prevents using a musical phrase as an alert – the change of height would sound horribly – as well as any voice, human or animal alert. How would blind people tell the street from the sidewalk if electric cars were talking or barking?
By giving automakers latitude to mark their alerts, NHTSA rules created a new form of design: acoustic automotive styling. Pedestrians and cyclists will not only hear the vehicle coming; they will know what type of car it is. For acoustic designers, electric vehicle pedestrian alerts and their rich in-cab sound information menus represent the dawn of a new era. “I feel lucky to be able to work on features that will influence how the world will sound,” General Motors creative sound director Jigar Kapadia told me.
Kapadia, who studied electronics and telecommunications engineering at the University of Mumbai and has a master’s degree in music technology from NYU, collaborates with Moore and others at GM’s sound lab in Milford, Michigan. . For each sound, the team comes up with around two hundred variations and then tests them on their colleagues in the jury room, until they’ve come up with a few finalists they can test on vehicles.
Kapadia compares the sound of an alert system to a scent. “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 fused together to bring out a cohesive organic sound, or a futuristic sound, based on the type of branding we’re focusing on.” He noted that the pedestrian alert on the 2023 Cadillac Lyriq, the first electric version of GM’s longtime luxury car, was made with a didgeridoo, an ancient Australian wind instrument based on the known musical interval. as the perfect fifth. However, for GM’s nine-thousand-pound electric Hummer, which recently went on sale, Kapadia said, “we wanted a more distorted sound.” He paused, then added, “Bold Hummer sound.” The Hummer’s forward motion alert made me think of church, when the organist launches into the next hymn. The backup sound resembles its dystopian twin.
At Ford Motor Company, to find out what car buyers thought electric vehicles should look like, engineers and consultants held “customer clinics” and launched a Facebook campaign. Judging by the number of responses, Ford fans were keen to make their opinions known. My own investigation, based largely on reading comments under YouTube videos of various branded EV sounds, is that most people think EVs should not look like ICE cars. Higher frequencies are thought to mean clean energy and software-driven intelligence; EVs should whiz and zoom like flying personal vehicles from sci-fi movies like “The Fifth Element,” “Gattaca,” “Blade Runner” and, of course, “Star Wars.” In many cases, in fact, Foley artists created the sound effects of these futuristic vehicles from recorded ICE noise. In Ridley Scott’s “Blade Runner 2049,” the twist is that Ryan Gosling’s flying vehicle looks like a broken down ICE clunker.