Traffic noise formula (Traffic Noise Overlay)

The calculations for the Traffic Noise Overlay follow the standard Calculation Method 1 (SRM 1).

$LAeq=E+C_o+C_r-D_a-D_l-D_b-D_m$

$D_l=0.01\cdot d^{0.9}$

$D_m=\max (0.0,3.5\cdot (1.0-e^{\frac{-0.04\cdot d}{h_s+0.75+h_c+0.75}}))$

where:

$LAeq$ = equivalent noise level (dB(A))

$E$ = calculated emission

$C_o$ = acceleration term on intersections (default = 0 dB(A))

$C_r$ = reflection term. This term is not used, and by default 0 dB.

$D_a$ = distance reduction

$D_l$ = air reduction

$D_b$ = surface reduction. This term is not used, and by default 0 dB.

$D_m$ = calculated meteorological reduction

$d$ = distance from the receiver to the source.

$e$ = Euler's number, approximated as 2.7182.

$h_s$ = Building datum height (DTM) of the noise source

$h_c$ = Building datum height (DTM) of the noise receiving cell.

Default values are taken from InfoMil [1]

Acceleration term on intersections

Accelerating on intersections can cause more noise. This value is only calculated for roads of category INTERSECTION. It is calculated as follows:

$C_o=1.4+\frac{Q_v+Q_t+Q_b}{Q_c+Q_v+Q_t+Q_b}$

where:

$Q_c$ = number of cars per hour

$Q_v$ = number of vans per hour

$Q_t$ = number of trucks per hour

$Q_b$ = number of buses per hour

Distance reduction

Distance reduction is computed as:

$D_a=10\cdot lo{g}_{10}(r)$

where:

$D_a$ = distance reduction

$r$ = shortest distance between the source and point of evaluation

Emission

Emission is computed as:

$E=10\cdot lo{g}_{10}(10^{\frac{Ec}{10}}+10^{\frac{Ev}{10}}+10^{\frac{Et}{10}}+10^{\frac{Eb}{10}})$

where:

$E$ = the combined noise emission

$Ec$ = the calculated noise emission for cars

$Ev$ = the calculated noise emission for vans

$Et$ = the calculated noise emission for trucks

$Eb$ = the calculated noise emission for buses

The emission per type of traffic is computed similarly, with values specific to the type of traffic. It is calculated as follows for car traffic:

$Ec=E_{c,start}+E_{c,mult}\cdot lo{g}_{10}(\frac{V_c}{V{0}_c})+10\cdot lo{g}_{10}(\frac{Q_c}{V_c})+\sigma +\tau \cdot lo{g}_{10}(\frac{V_c}{V{0}_c})$

where:

$E_{c,start}$ Emission start value. Configurable with model attribute Emission start (Traffic Noise Overlay). See also: InfoMil [2]

$E_{c,mult}$ Emission factor. Configurable with model attribute Emission mult (Traffic Noise Overlay). See also: InfoMil [3]

$V_c$ = The traffic type's speed, configured in roads with attribute TRAFFIC_SPEED.

$V{0}_c$ = The traffic type's reference speed, configured per traffic type using the model attribute V0.

$Q_c$ = number of cars per hour, configured with Function Value Cars per hour (Function Value)

$\sigma$ = road surface correction value at reference traffic speed. Configurable in roads with attribute TRAFFIC_NOISE_SIGMA

$\tau$ = road surface correction factor per 10 km/hour deviation from reference traffic speed. Configurable in roads with attribute TRAFFIC_NOISE_TAU

Notes

• If traffic amount is a single value, it applies to all defined hours. If it is an array of values, each index corresponds to its respective hour.

See also

• Traffic Noise Overlay

References