How loud are cars in dB?
Car noise varies by source and speed. Rough ranges: exterior noise is typically about 50–60 dB(A) when idling and about 70–85 dB(A) during highway pass-bys; inside the cabin, noise is usually around 40–65 dB(A) depending on speed and wind. The decibel scale is logarithmic, so a 10 dB change roughly doubles perceived loudness.
Understanding decibels and how measurements work
Decibels (dB) quantify sound pressure, but for human hearing a-weighted decibels (dB(A)) are used to reflect how loud a sound is to people. Measurements depend on distance from the source, the environment, and the measurement method. The values cited here are typical real-world ranges for common driving conditions and vehicle types.
Exterior noise levels
Below is a snapshot of typical exterior noise levels you might observe from common driving scenarios, expressed in dB(A).
- Idle engine/exhaust: about 50–60 dB(A) at a short distance from the vehicle.
- Starting and low-speed acceleration in urban streets (roughly 20–40 km/h): about 60–70 dB(A).
- City driving at moderate speeds (around 50–60 km/h) with a pass-by: about 65–75 dB(A).
- Highway driving around 100 km/h: about 70–85 dB(A) depending on tires and surface.
- Electric vehicles (EVs): at very low speeds, noise is much lower, but tire/road and wind noise dominate at higher speeds, typically around 60–70 dB(A) externally.
These figures are indicative; actual measurements vary with vehicle design, tire selection, road surface, wind conditions, and sensor placement. Modern regulations also aim to limit these numbers for new cars.
Interior noise levels
Inside the cabin, noise levels are influenced by powertrain, wind, tires, and vehicle insulation. The ranges below reflect common experiences with conventional and electric vehicles.
- Idle cabin noise (engine on): about 40–50 dB(A) in many modern cars.
- City driving with windows up: about 50–65 dB(A).
- Highway driving with windows up: about 60–70 dB(A), with EVs often quieter at low speeds but similar tire/wind noise at highway speed.
- EV interiors: typically lower than internal combustion cars at low speeds, but highway tire/road noise can bring cabin levels into the 60–70 dB(A) range.
Interior noise can be affected by vehicle stiffness, sealing efficiency, HVAC operation, and wheel/tire characteristics. Even small changes in speed or wind direction can shift the cabin soundscape noticeably.
What affects car noise
Several design and operational factors determine how loud a car is, both outside and inside the cabin. The main influences include:
- Powertrain type and exhaust design (gasoline vs. diesel vs. electric).
- Tire type, tread pattern, and wear, plus road surface texture.
- Aerodynamics and wind noise at speed (airflow around the body and mirrors).
- Vehicle speed and acceleration profile.
- Suspension and chassis design, which affect road noise transmission.
- Window and door sealing, climate control operation, and overall cabin insulation.
Understanding these factors helps explain why two similar cars can sound quite different, and why a quiet EV still sounds noticeable at highway speeds due to tire and wind noise.
Regulatory context
Regulators around the world set maximum allowable exterior noise for new cars, using standardized tests to ensure comparability across makes and models. The exact limits vary by region and vehicle class, but the intent is to curb road noise in urban areas while balancing performance and safety.
- European Union (UNECE Regulation 51): pass-by noise limits depend on vehicle class and test method; modern passenger cars typically must meet limits in the mid-to-upper 70s dB(A) in standard tests, with some variation by speed and configuration.
- United States: federal noise emission standards apply to new motor vehicles, with certification tests that include exterior noise measurements; compliance rules vary by vehicle type and test procedure.
Standards are periodically updated to reflect advances in engineering and public-safety goals. For the most accurate, region-specific figures, consult the latest regulatory documents in your area.
Summary
Car noise spans a broad range. Exterior, idle noise from typical passenger cars sits around 50–60 dB(A), climbing to roughly 70–85 dB(A) during highway pass-bys. Inside the cabin, sound levels are usually lower, around 40–70 dB(A) depending on speed, wind, and insulation. Electric vehicles tend to be quieter at low speeds but tire and wind noise dominate at higher speeds. The decibel scale is logarithmic, so perceived loudness does not increase linearly with the numbers. Regulatory standards aim to curb road noise without compromising vehicle performance, and actual experiences will vary by model, conditions, and maintenance.
