Enter traffic volume (vehicles per hour), percent heavy trucks, speed, and distance from the road into the calculator to estimate the outdoor road-traffic noise level as an hourly equivalent A-weighted level (LAeq,1h) in dB(A).
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Road Noise Formula
The following simplified screening formula (similar to what the calculator uses) can estimate an outdoor hourly A-weighted equivalent level from road traffic. Logarithms are applied to dimensionless ratios (e.g., V/60), not to quantities with units.
L_{Aeq,1h}\approx 75+10\log_{10}\!\left(\frac{Q_{\text{eff}}}{1000}\right)+30\log_{10}\!\left(\frac{V}{60}\right)-10\log_{10}\!\left(\frac{D}{50}\right)+10\log_{10}(N_{\text{lanes}})+C_{\text{pavement}}+C_{\text{ground}}Variables (screening estimate):
- LAeq,1h is the estimated hourly equivalent A-weighted level (dB(A))
- Qeff is the “effective” traffic volume per lane (veh/hr), adjusted for heavy trucks (a rough energy-weighting)
- V is the vehicle speed (mph)
- D is the distance from the near lane to the receiver (ft)
- Nlanes is the number of lanes in the same direction (assumed similar contribution per lane in this simplified model)
- Cpavement is an approximate pavement adjustment (e.g., open-graded asphalt ≈ −3 dB)
- Cground is an approximate ground adjustment (e.g., “soft” ground ≈ −1.5 dB)
In this model, 75 dB(A) is an empirical reference level at Qeff=1000 veh/hr per lane, V=60 mph, and D=50 ft for average pavement and hard ground. The 10·log10(…) terms add traffic energy, and the distance term uses a line-source style attenuation (about 3 dB per doubling of distance). This is intended as a quick estimate; for design/compliance, use a full traffic-noise model and site-specific inputs.
What is Road Noise?
Road noise is the sound generated by vehicles traveling on roadways. It is a type of environmental noise that can be disruptive to nearby residents and wildlife. Factors that contribute to road noise include vehicle speed, traffic volume, road surface, tire design, and the distance from the road. Understanding and calculating road noise levels can help in the design of noise barriers and other mitigation strategies.
How to Calculate Road Noise?
The following steps outline how to estimate the Road Noise Level.
- Determine the traffic volume per lane (Q) in vehicles per hour (veh/hr) and the percent of heavy trucks (if known).
- Determine the average vehicle speed (V) in miles per hour (mph).
- Determine the distance from the near lane to the receiver (D) in feet (ft).
- Use the formula above (with the reference ratios V/60, D/50, and Qeff/1000).
- Calculate the estimated outdoor noise level as an hourly equivalent A-weighted level (LAeq,1h) in dB(A), then compare with the calculator above.
Example Problem:
Use the following variables as an example problem to test your knowledge (assume 1 lane, average pavement, hard ground). Using the simplified screening formula above, the result is approximately 73.2 dB(A).
Traffic volume per lane (Q) = 1000 veh/hr; Heavy trucks = 8%
Speed (V) = 55 mph; Distance from the road (D) = 100 feet
