Why Are EVs Quieter than Petrol Cars?
It’s no secret that EVs can sneak around town without drawing the attention of people nearby. Petrol cars on the other hand, especially performance ones, can be heard approaching from several meters away. But why is there such a disparity between them in terms of noise pollution?
Internal combustion engine cars usually emit at least 70 decibels of noise at low speeds. Their mode of operation requires the use of a mixture of fuel and air that are made to combust in each cylinder. These timed explosions cause the up and down movements of the pistons.
The exhaust gases that are created from these explosions are expelled via the exhaust manifold and travel throughout the exhaust system, then the muffler before being released into the atmosphere. Besides combustion and resonance of gases leaving the exhaust, there are several other moving parts within the system that cause the overall operational noises of an ICE engine.
In the case of electric vehicles, the opposite is true. Instead of relying on thermodynamics, which include the combustion process to operate, EVs rely on chemical reactions as their source of power. Their propulsion system consists of an electric motor, powertrain, and battery pack.
Through a chemical reaction within its batteries, EVs create electricity that’s then used to power its electric motors. These motors consist of a stator and rotor, as their main components. Electricity is supplied to the stator’s coils to create rotating magnetic fields.
This causes the rotor to spin as it’s attracted by these rotating magnetic fields. Granted, we are oversimplifying the process, but the basic idea here is that electromagnets, rotational movements of a motor shaft and other components in the powertrain cause far lower noise levels than the overall output of an ICE engine.
In general, EVs are so quiet that the only audible noise you’d notice when they approach is the sound from their tyres. This whisper quiet mode of operation is dangerous especially for pedestrians who are unaware of their presence. This is why many manufacturers add artificial noises to their EVs when they are moving.
The EU has introduced regulations that ensure EVs must produce at least 56 decibels of sound at low speeds. This is equivalent to the noise level of a regular home appliance. Even at low speeds, an EV is still significantly quieter than an ICE one.
As such, choosing EVs over ICE cars will help reduce overall noise pollution as well as the emission of harmful gases in congested cities. At this point in time, the benefits they offer in the short term outweigh the drawbacks that they will cause over their entire lifespan.
