Silent Operation of Electric Vehicles
The automotive industry is going through a historical transformation from the noisy dominance of internal combustion engines to the futuristic silence of electric vehicles. Although this technological evolution allows us to take a giant step towards sustainability by reducing the noise pollution of our cities, it is completely rewriting the safety dynamics on the roads.
Our driver reflexes shaped by engine sound for over a century and the auditory expectations of pedestrians in traffic are now being put to a new test. In order to build an inclusive road culture that protects vulnerable road users such as pedestrians and cyclists, it is essential that we manage this silence correctly; otherwise, the price of this silence can be an unexpected crash.
So, what exactly lay behind the engine noise we are accustomed to, and what kind of risks does this new, silent nature of electric vehicles bring along both on the street and in the driver cabin? Here are all the details regarding the silent world of electric vehicles at the exact point where technological simplicity intersects with our perception of safety...
1. Why Do Internal Combustion Vehicles Make Noise?
The noise of Internal Combustion Engine (ICE) vehicles is a result of the intense mechanical and chemical processes inherent in their nature:
Controlled Explosions: The air and fuel mixture in the cylinders inside the engine block is continuously ignited or detonated under high pressure. The main source of the sound we hear is these consecutive, mini explosions.
Moving Mechanical Parts: Pistons, crankshafts, camshafts, and valves move thousands of times per second. The interaction and friction of these metal parts create significant mechanical noise.
Exhaust Systems: Waste gases produced as a result of combustion are expelled from the engine at high pressure. Even though mufflers reduce this sound, the exit of gases from the exhaust pipes always produces an audible hum or rumble.
2. Working Principle and Silence of Electric Vehicles (EVs)
Behind the almost gliding silent movement of electric vehicles lies mechanical simplicity and electromagnetism:
No Explosions, There is Magnetism: EVs get their power from electrons transferred from the battery to the electric motor. Movement is provided not by combustion, but by magnetic fields within the motor pushing and pulling each other.
Minimum Moving Parts: While a traditional engine has hundreds of moving parts, an electric motor basically has only a rotating "rotor". There are no heavy mechanical processes where metal rubs against metal.
No Need for an Exhaust: Since no fuel is burned, there is no gas to be expelled, and therefore no exhaust system and the pressure sound it creates.
3. Average Decibel (dB) Comparison of the Two Vehicle Types
The difference in silence becomes apparent especially at low speeds (0 to 30 km/h) and during moments of acceleration. When high speeds are reached (50 km/h and above), decibel levels approach each other because tire friction and wind noise become dominant in both vehicle types.
The average values for low speed urban scenarios are as follows:
- Internal Combustion Vehicle : 65 to 75 dB
- Electric Vehicles : 35 to 45 dB
4. Warnings Regarding Silence in User Manuals
Electric vehicle manufacturers are aware that this technological advantage can turn into a risk in the city. The user manuals of the vehicles generally include the following safety and awareness warnings:
- Requirement for Visual Confirmation:Drivers should not just expect pedestrians to see the vehicle, especially in school zones, parking lots, and narrow streets, but must ensure they are noticed by making eye contact with pedestrians.
- Emphasis on Crash Risk:Because the vehicle approaches very quietly, visually impaired individuals, pedestrians wearing headphones, or distracted cyclists may not notice the vehicle. Manuals request extra caution by stating that the risk of a crash is higher when maneuvering at low speeds compared to standard vehicles.
- Cautions for Reversing Maneuvers:Since the silence of an approaching vehicle in reverse gear can be even more dangerous, it is stated that active driver observation is essential in addition to rearview cameras and sensors.
- Vehicles Left Running:Drivers may leave the vehicle thinking it is turned off because they do not hear an engine sound. This situation can pave the way for safety vulnerabilities and can also cause the vehicle to move if a child or a pet left inside accidentally touches the pedals.
- Unintended Acceleration and Crash Risk:The driver may think that the system is not activated or the vehicle is not running because they do not hear a standard starter or engine sound after pressing the start button. Touching the gas pedal with the reflex to test the vehicle or measure the response of the engine, combined with the characteristic of electric motors to provide instant high torque without delay, causes the vehicle to lurch forward or backward with unexpected force. This misconception can cause a severe crash with bystanders or structures in parking lots or narrow spaces.
5. The Sound Emitting System in Electric Vehicles: AVAS
To make the crash risks created by silence compatible with a tolerable and forgiving road infrastructure, AVAS (Acoustic Vehicle Alerting System) has been developed.
- How It Works:Through speakers placed at the front and rear of the vehicles, an artificial sound is emitted to the outside while the vehicle is traveling at low speeds (generally between 0 to 20 km/h or 0 to 30 km/h) and when it is put into reverse gear.
- Nature of the Sound:This sound is not an annoying horn, but a futuristic frequency whose pitch and tone change according to the speed of the vehicle so that pedestrians can perceive that a vehicle is approaching by accelerating or slowing down.
- Legal Requirement:In many regions, primarily the European Union and the United States, the active use of AVAS in all new electric and hybrid vehicles below a certain speed has become a legal standard (for example UN ECE R138 regulation) and cannot be completely turned off manually by the driver.