When I get situated in the driver’s seat of my Tesla Model Y, my initial auditory experience is stillness and a vacuum of sound. The motor emits neither noise nor vibration. Engaging the automatic transmission into Drive mode sparks a visual confirmation on the touchscreen but has no accompanying functional sound. When I accelerate, I do not hear any technical audible indication, although some might say there is a gentle whir from the two electric motors. When I release the accelerator pedal and engage regenerative braking, a very low, almost indecipherable, sound occurs. Around 30 mph, tire noise starts to mask any light soft motor sounds and, with growing speed, wind noise takes over. At highway speeds, road and aerodynamic noise dominates any motor sound.
Gentle and nearly absent EV motor sounds contrast with prevalent, culturally inscribed connotations of internal engine power. Part of US identity is unalterably associated with the roar of the engine, those purrs and rumbles and growls that we think of as essential to what it means to drive.
Yet the quiet Model Y is no slacker in acceleration or high end speed compared to most other vehicles on the road. Nor are other EVs much less powerful, as a general rule.
How is the historical expectation of rich auditory sound diminished by driving an EV? Is noise from a car “so yesterday?” Will EVs with silent motors help to break with automotive conventions of pounding sound and power?
Among multiple rationales for purchasing an EV, appeals to the 5 human senses and natural sounds continue to be important to consumers. Studies indicate that, consistent with a particular frequency band, automotive consumers expect familiar auditory experiences.
As an iconic article in Sound Studies notes, it takes work to “decouple the symbolic links between speed, societal dominance, and loud sound, on the one hand, and the building of new links between (electric) engine power and silence, on the other.” Research in the mid-2010’s proposed relevant sonification strategies to augment the interior sound environment by associating vehicle dynamics with synthetic auditory cues.
By 2022, it turns out that acoustical and perceptual spatial characteristics of the car soundscape are more than just satisfying: the spatial attributes of sound sources are fundamental to improve the perceptual coherency of our driving.
Acoustic Vehicle Alerting System
Government agencies have imposed regulations on EVs and hybrids with which automakers must comply, called acoustic vehicle alert systems (AVAS). This acronym refers to exterior sounds emitted from the vehicle. The AVAS sound provides similar information to internal combustion engine sounds for pedestrians, letting them know a vehicle is nearby, and what it is doing.
AVAS is a required accessory for EVs in most countries. The AVAS system generates sound for nearly silent EVs to improve the safety of vulnerable road users (VRU) such as pedestrians, cyclists, and children.
Artificial vehicle sounds are generated using loudspeakers or actuators through the vibration of the vehicle’s structural elements proportional to vehicle parameters such as velocity, gas pedal position, and gear. Just as traditional vehicles often make a slightly different sound when reversing, the AVAS system can also amplify a unique reversing sound to inform VRU’s ego path, even in the absence of visual cues.
GM Engineers Compose the EV Auditory Experience
In acoustically treated rooms at GM’s Milford Proving Ground, they’ve gathered folks with backgrounds in classical music, electronics, and wellness. They’re coalescing to create what a company press release calls “EV-specific sounds with an engineer’s brain and a musician’s heart.” The advanced audio design they have been reimagining is “the soundtrack to our future all-electric drives.”
Alerts and chimes, or functional safety sounds, are another facet of EV sound design, composed with the intention of blending into the background. The goal is for customers not to notice the sound itself but, rather, the message behind it. Take, for example, the “fasten seat belt” alert. When the alert goes off, the customer should receive the message that they need to buckle their seat belt rather than notice the sound itself.
“Sound design and sound engineering is really a fusion of regulatory needs and artistic design,” says Doug Moore, a GM global regulatory sound and vibration engineer. “We want purposeful and pleasing exterior sound and a relaxing experience for customers in the interior. It all comes down to making our EVs safe and enjoyable.”
Interestingly, these GM sound designers are creating sounds that are distinguished, model to model. That means a GMC Hummer EV will not sound like a Cadillac Lyriq. It starts with ideating a brand’s persona and composing accompanying and unique EV model sounds. Engineers work with performance, systems, noise, and vibrations so the different sounds emerge for each model.
Cadillac-specific EV sounds: These include layered textures of major chords combined with low frequency tones that add to the vehicle’s audible character. Cadillac’s robust sound system hardware and ample speakers allow engineers to take creative liberties in crafting sounds that enhance the luxury interiors of the vehicles while also providing a pleasant experience for passengers. The sound design of the Hummer EV is dynamic, distorted like a loud electric guitar, and confident.
Hummer-specific EV sounds: The GM press release foregrounds the Hummer EV’s available “Watts to Freedom” mode, which offers 0-60 mph acceleration in approximately 3 seconds on the Edition 1 pickup. When this feature is engaged, a choreographed visual illuminates the LED dash, showing the Hummer EV lowering. When the driver puts their foot on both the accelerator and brake pedals, the visual shows the torque and power building. The sound that accompanies the display is a combination of layered, synthesized sounds that signal that the Hummer EV is preparing to activate Watts to Freedom. One engineer worked with noise and vibration engineers to create a low, rumbling trigger sound and a second, distinct sound as the EV super truck engages the max acceleration driving mode.
GM’s noise and vibration engineers also craft AVAS with different tunings and calibrations for each of GM’s brands, as both safety and brand personality are at the forefront of this auditory decision making. As each new EV enters GM’s portfolio, the company says that customers can expect a cache of new sounds that complement the brands and vehicles’ identities.
Final Thoughts about Creating Auditory Experiences for EV Drivers
In early pilot studies, users reported that EV auditory stimulus lacked blending with the surrounding natural sound field of the vehicle and the artificial character of the sound itself. The challenge was — and continues to be — to integrate such sound feedbacks in the car interior soundscape in natural ways by adjusting both timbre and spatial parameters.
Artificial engine sound creates synthetic sounds and influences driving behavior in positive ways. It supports quicker responses through accentuating situational awareness. With EVs on the rise, sound designers are getting a chance to create the auditory experience of the 21st-century. Because EVs can sound like anything designers envision, future EV drivers are likely to experience a wide variety of fun and instructive auditory stimuli.
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