The air-polluting, carbon emitting standard liquid fuel combustion engine vehicles have an audible engine sound, even when traveling at low speeds. Pedestrians and other vehicle drivers recognize a moving vehicle via sight and sound coming from tires and other emitted noise when the vehicle may be out of sight.
Electric vehicles (EV) do not emit an engine sound. Hybrid electric vehicles (HEV) or plug-in hybrid electric vehicles (PHEV) move virtually silent when travelling at low speeds and before the conventional internal combustion engine (ICE) kicks in. These vehicles are difficult to hear when travelling at speeds less than 19 mph. At greater speeds, tire sound becomes dominant.
See my articles on the death of a person during a trial testing of an Uber autonomous EV in Phoenix Autonomous vehicles: The electronics road to making them safe and also my Formula E article on Experiencing the Formula E electric race car: Sounds of Silence. The Uber accident and death strongly demonstrates the need for sound in moving EVs that is absolutely needed on roads, streets and highways and, as a minor aside, the Formula E article begs the possible need for a more ‘racing car’ sound options for the spectators.
Analog Devices, Inc. (ADI) has developed a new embedded system for generating engine sound for electric (EV) and hybrid electric vehicles (HEV).
The ADSP-BF706 which is a DSP which can be coupled with their http://www.analog.com/en/design-center/processors-and-dsp/evaluation-and-development-software/evwss.html#dsp-overview Electric Vehicle Warning Sound System (EVWSS) firmware which enables automobile manufacturers in North America and other global regions to comply with future safety regulations mandating external engine sound for EVs and HEVs travelling at low speeds.
Here are the EU regulations for autonomous EVs Addendum to UN Regulation No. 138 and Commission Delegated Regulation (EU) 2017/1576
ADI has a complete hardware and firmware reference design that can be scaled for high performance with the ADSP-BF706 or entry level applications with the ADAU1450 Digital Audio Processor. The ADSP-BF706 can also be used to create in-cabin engine sound to contribute to an improved driving experience for vehicle owners.
The Processing blocks on the Blackfin plus Processor (Image courtesy of Analog Devices)
ADI’s Sigma Studio Integrated Development Environment (IDE) enables OEMs to graphically tune the audio sound when using the ADAU1450. This allows sound engineers with minimal programming experience to optimize audio performance with a faster development time.
A low-cost CAN software stack runs on the ADSP-BF706 to help customers quickly build automotive-grade prototypes.
EVWSS Library functions include Pitch control, Frequency and Amplitude modulation, Audio mixing in Slew, and Playback of WAV files.
See this AN-1552 Application note entitled Electric Vehicle Warning Sound System