• Construction Noise
  • Handbook
  • RCNM Version 1.1
  • RCNM Version 2.0
  • Special Report
• Measurement
• Noise Barriers
• Noise Compatible Planning
• Regulation and Guidance
• Resources
• Tire Pavement Noise
• Traffic Noise Model
• Training

Roadway Construction Noise Model User Guide

5. Calculations in the RCNM

The RCNM uses the primary equation described in the CA/T Construction Noise Control Specification 721.560 [1] for the construction noise calculations.

5.1 Metric Calculation

LmaxCalc = selected_Lmax - 20log(D/50) - shielding (1)

where

selected_Lmax is the "Spec" or "Actual" maximum A-weighted sound level at 50 ft., listed in Table 1 for all pieces of equipment, in dBA, D is the distance between the equipment and the receptor, in feet, shielding is the insertion loss of any barriers or mitigation, in dBA (see Appendix A).

Leq = LmaxCalc + 10log(U.F.%/100) (2)

where

U.F.% is the time-averaging equipment usage factor, in percent (see footnote 1 on p 7).

L10 = Leq + 3 dBA adjustment factor (3)

The RCNM calculates L10 by adding 3 dBA to the Leq, where the 3 dBA default L10 adjustment factor was empirically derived by comparing extensive CA/T construction noise data. This adjustment factor may be changed in the RCNM at the user's discretion.

5.2 Exceed Calculation

Daytime Lmax Exceedance = LmaxCalc - Daytime Lmax Limit (4)

Daytime Leq or L10 Exceedance = Leq or L10 - Daytime Leq or L10 Limit (5)

Evening Lmax Exceedance = LmaxCalc - Evening Lmax Limit (6)

Evening Leq or L10 Exceedance = Leq or L10 - Evening Leq or L10 Limit (7)

Nighttime Lmax Exceedance = LmaxCalc - Nighttime Lmax Limit (8)

Nighttime Leq or L10 Exceedance = Leq or L10 - Nighttime Leq or L10 Limit (9)

5.3 Totals Calculation

The Total values in the Results section are determined in the following manner:

1. Total Leq = 10*log(∑(individual equipment Leq values³))
2. Total L10 = 10*log(∑(individual equipment L10 values³))
3. Total Lmax = Maximum among individual equipment Lmax values
4. Total noise limits and limit exceedances:
   1. Determine whether or not total is impact or non-impact
      1. If all the equipment is non-impact, label the total as non-impact.
      2. If all the equipment is impact, label the total as impact.
      3. If the equipment is mixed non-impact and impact, label the total as non-impact.
   2. Determine total noise limits and limit exceedances the same way as with individual pieces of equipment (see Section 5.2), only use the calculated total sound levels (Total Leq or Total L10) and the impact or non-impact label according to the criteria specified in i through iii.