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Hybrid and electric vehicles are so quiet pedestrians can’t hear them coming. To protect pedestrians, since July 1, the European Union requires electric and hybrid vehicles at speeds below 20 km/h (12 mph) to have Acoustic Vehicle Alerting Systems (AVAS).

In the U.S, the National Highway Traffic Safety Administration (NHTSA) requires new electric and hybrid vehicle purchases made after September 1st, 2019 to emit a warning noise below 18.6 miles per hour (30 km/h).

AVAS is still in its early stages of development. Automotive suppliers have developed products, while automakers are using sounds as part of a branding creative experience. In the future, sounds could become more intelligent and personalised.

Available Technology from Suppliers

To meet mandates automotive suppliers have created pedestrian acoustic systems with flexible features for automakers.

HARMAN’s HALOsonic, External Electronic Sound Synthesis (eESS) system is so flexible the type of sound  can be anything such as a V6 engine, a drone sound or something from Star Wars, says Rajus Augustine, senior director product strategy and planning, car audio SBU at HARMAN.

“The sound has to be easily recognized as a vehicle by pedestrians and people. It’s a great opportunity for sound to reflect the DNA of the vehicle,” says Augustine who reports part of the engineering problem of external sound devices is that to keep the system away from the heat of the engines. A benefit of HARMAN’s HALOsonic platform is that it enables Over-the-Air OTA updates, changing of profiles of different cars as well as different sounds for different countries or continents.

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Another very important sound for electric vehicles is something called psycho-acoustic sounds within the vehicle. For example, in a gas-powered vehicle when the engine is turned on the driver knows that the car is running but in an electric vehicle there is no sound when the engine starts therefore there usually has to be some kind of welcome sound so that the driver knows that the car is running.

Currently, Continental’s AVAS products range from high-performance to more budget-friendly versions. These include something simple, like a loudspeaker, which is an ECU combination capable of hosting one or two different sound files, up to a high-end version which can host many different or complex sound files in combination with loudspeakers or even actuators that create sound by vibrating surfaces in the vehicle. 

“This high-end version really opens up the possibility for customization at the carmaker level to have different sounds for different situations, like stopping, accelerating, going forward, going in reverse, to audibly communicate the vehicle’s action. In theory, this means that carmakers could choose to allow end-consumer customization as well,” says Kent Young, manager of business development, passive safety and sensorics for Continental, North America.

Automaker EV Sounding Boards for Innovation and Creativity

Automakers such as BMW and Nissan are making EV and hybrid sounds sounding boards to innovation.

Nissan began offering pedestrian warning sounds with the Nissan LEAF in 2011 designed by Toshiyuki Tabata and various composers that they called “beautiful and futuristic.”

Joel Beckerman, founder of Man Made Sound who designed the sound ‘Canto’ for Nissan’s future fleet of EVs told Auto futures that EV sounds should be about “Alerting people without scaring them, and not adding unnecessary noise to our environment.”

BMW’s acoustic pedestrian warning system has been available as an option in Europe since 2013, says Martin Tholund, spokesperson for BMW products and innovation.

Electrically powered BMW models are enveloped by an unmistakable sound that was specially developed for the BMW brand. The development goal was to implement the warning function without irritating pedestrians. Each model has its own sound characteristics, an acoustic fingerprint, due to its construction and the materials used. As a result, the models also sound differently to the listener’s ear.

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“The sound of our acoustic pedestrian protection is continuously improved by our acoustic engineers in favour of less exterior noise and more acoustic comfort in the interior, without minimising the important warning function,” says Tholund. 

The BMW Vision M NEXT concept showcases BMW’s sound of future electric driving. The e-sounds of the BMW Vision M NEXT were co-created by renowned film composer Hans Zimmer and BMW sound designer Renzo Vitale.

Zimmer, in composing the sounds, uses the accelerator as a ‘performative element’ to invoke emotion. BMW IconicSounds Electric is the brand name for future BMW electric vehicle sounds, a product for BMW drivers who want to increase their electric driving enjoyment with selected sounds, says Tholund.

So far, US legislation has not regulated the possibility that drivers could personalise their EV sounds or automakers to offer alternative sounds. In response to a petition to allow vehicles to be manufactured with a suite of driver-selectable pedestrian alert sounds, NHTSA reported that it “is neither granting nor denying that request.”

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The Future of More Intelligent EV Sounds

EV drivers who would like EV sounds to sound entirely like music will be disappointed, the pedestrian warning should be the major reason for EV sounds, says Kota Kobayshi, design lead at ustwo.

“Our research shows when the EV sound sounds like music, it doesn’t communicate emergency. It needs to feel like noise to protect pedestrians,” says Kobayshi.

Kobayashi envisions future electric vehicle sounds to be smarter than the sounds of internal combustion engines to increase the safety of pedestrians. He suggests different warning sounds depending on the severity of the situation, different speakers broadcasting sounds based on the location of pedestrians and sounds based on the surrounding environment.

Another future option could be in the aftermarket for electric and hybrid vehicles with personalised EVTones.

“It’s like mobile phone ringtones for electric vehicles,” says Robert McDowell, founder of EVTones that will offer a variety of directional EV sounds that change according to vehicle speed.

EVTones allows drivers to express themselves and be compliant with government regulations, says McDowell. The driver can play a loud engine roar inside the car, while the outside pedestrian sound is at the legal level, for what he calls “outside compliant inside defiant.”

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