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Pass-By of individual Vehicles

CadnaA offers to calculate for roads, railways, and line sources the time history of the sound pressure level that would result from a single vehicle with a specified emission passing by, according to the selected standard. The command Pass-By Level in the context menu of those types of line source is only available if at least one receiver has been inserted. When calculating the maximum level, a directivity assigned to the receiver is taken into account (see Receiver, Directivity).

For example, generating this pass-by level history enables to check:

  • whether the effect of a noise-control device, such as a barrier, would be sufficient for all affected partial areas, or
  • which noise reduction may be expected by providing a reflecting building facade with absorbent cladding, or
  • by which amount the sound pressure level resulting from single motor vehicles traveling by is reduced if - for example - a zone with a speed limit of 30 km/h is established in an ordinary inner-city street.

Note

The feature „Pass-By Level“ is not available in conjunction with the angle-scanning method (see General Tab).

Dialog options

Receiver

Select the name of the receiver point where the pass-by level shall be calculated.

Source Type

The available option depend on the type of object from the context menu of which the command Pass-By Level was selected.

all object types: User-defined

The option „user-defined“ is always available (for roads, railways and line sources). In this case, all parameters can be specified individually. Subsequently, the source is running along the route with the specified speed and sound power level.

Object „Road“: light or heavy

The sound power level of cars („light“) or trucks („heavy“) is determined based on the speed specified on the dialog Road (see below). The sound power levels correspond with the specifications in RLS-90 RLS-1990.

Object „Railway“: train class

On the list box all train classes from the dialog Railway are listed. When selecting a specific train class the sound power level is calculated according to the specifications of Schall 03 (1990) S03-1990 (see below).

Emission/Sound Power Level

Object „Road“

The sound power level for cars („light“) and trucks („heavy“) calculates from:

\(L_{WA}(1\:car) = L_{m,E}(1000\:car/h)+19.2dB+10\lg(\frac{v_{car}}{1 km/h})\)

\(L_{WA}(1\:truck) = L_{m,E}(1000\:truck/h)+19.2dB+10\lg(\frac{v_{truck}}{1 km/h})\)

On the following table, the sound power level for cars and trucks is given as a function of the speed are listed addressed to a single vehicle of each category based on the emission value Lm,E according to RLS-90 (see RLS-90).

Vehicle Category Emission Parameter Speed in km/h
30 50 80 100 120
light (car) Lm,E 58,5 60,8 64,8 67,2 69,4
LWA 92,5 97,0 103,0 106,4 109,4
heavy (truck) Lm,E 71,5 74,3 76,9 - -
LWA 105,5 110,5 115,1 - -

Examples:

  • car at 100 km/h: \(L_{WA}(1\:car))67.2+19.2+10\lg(100)=106.4dB(A)\)

  • truck at 80 km/h: \(L_{WA}(1\:truck))76.9+19.2+10\lg(80)=115.1dB(A)\)

Object „Railway“

After selection of a train class the sound power level calculates from:

\(L_{WA}(1\:train)=L_{m,E}(1\:train)+19.2dB-\text{Railway Corr.}+10\lg(\frac{v}{3.6})+10\lg(16h*3600\frac{s}{h})\)

with

  • Lm,E: emission level at 25 m from the railway’s axis (according to Schall 03)
  • 19.2 dB: relationship between the emission level Lm,E and the sound power level per unit length PWL’ (according to Schall 03)
  • Railway Correction: When the option „Strictly according to Schall 03“ is enabled (see Section 6.2.11.1), a correction of 5 dB is considered. Otherwise, the value entered on tab „Railway“ is used.
  • v: train speed in km/h
  • 16 h: A time correction is applied as the emission in Schall 03 refers to a time interval of 16 hours. This correction is a constant.

Thus, the sound power level per unit length LWA’ for a single train with train length l (m) is:

\(L_{WA}'(1\:train)=L_{WA}(1\:train)-10\lg(\frac{l}{1m})\)

Example

emission of an ICE train with a railway correction of 5 dB:

The sound power levels LWA and LWA’ result from:

\(L_{WA}(1\:train)=50.2+19.2-5+10\lg(\frac{250}{3.6})+47.6=130.4 dB(A)\)

\(L_{WA}'(1\:train)=130.4-10\lg(\frac{420}{1m})=104.2 dB(A)\)

Object „Line Source“

When selecting the command Pass-By Level from the context menu of a line source, the sound power level can be entered directly after selecting the option „user-defined“.

Sample Time

Both, the sampling time and the speed determine the section lengths through which the fictitious vehicle or the source moves from one location to the next. A sampling time of 1 s may be sufficient to check for the required calculation time, a value of 0.1 s may be appropriate to represent a level record showing all level variations due to shielding and reflections.

Driving direction negative/positive

The direction of traffic can be specified with respect to the direction in which the road was inserted. „Positive“ (pos) means the driving direction is from the first to the last point of the geometry, „negative“ (neg) vice versa.

Append to Diagram

By this option several pass-bys can be simulated consecutively with their level history getting appended to each other. Keep the dialog Pass-by Level displayed and mark once again the same object or a different one with the right mouse button and select again Pass-By Level from the context menu. Activate the option „Append to Diagram“ and select for the driving direction „negative“ or „positive“.

Pass-By Diagram

By clicking and dragging the mouse arrow inside the diagram with the left mouse button pressed in a horizontal direction the vehicle symbol will be moved along the source line in the graphics.

Alternatively, select a value from the Animation menu. The pass-by then will start running automatically with the selected speed.

Auralisation

Hardware requirement: sound card and loudspeaker or headphones

On the menu Auralization|Properties the saved sound file of the relevant process is opened after selection of a sound type in the list box and is reproduced - regarding volume - according to the calculated time history of the pass-by level.

3D-Auralisation

By the option „3D-Auralization“ the Doppler effect - when switching from approach to departure (by „Direction of Motion“ - will be simulated in a realistic way.

Listening direction at Receiver Point

Automatically to source: viewing directly towards the source (with the shortest distance)

Direction (°)

view at the given angle towards the source, relative to the x-axis

Calibration

Select the desired volume from the list box and adjust the corresponding playback on your audio device.

Example

Example

Path: Examples\ Sources\Road\Pass-By.cna

  • Test the Pass-By with a simple arrangement as in the following figure.

Road with buildings and a receiver

  • Open the context menu by clicking the road axis with the right mouse key and select the command Pass-By Level.
  • From the list box „Receiver“ select the desired receiver for which the pass-by level shall be calculated - in our example IP1.
  • In the next box „Source Type“ select „light“.
  • Enter a length of 5 m.
  • Adjust the sampling interval to 0.1 s.
  • After confirmation with OK the diagram opens with the calculated levels time history. The calculation time depends on the complexity of the project.

For a light vehicle calculated level time-history

  • Now move the mouse cursor in the diagram and press the left mouse button. On this position a vertical cursor line appears, whose time and sound pressure level is indicated in the upper dialog bar and a symbol (black box) indicates the vehicle’s position on the road in the graphic, in the driving direction on the road.
  • When dragging the cursor line horizontally ins the diagram the vehicle’s symbol will move along the road.
  • Alternatively, select a value from the Animation menu.

Regarding the vehicle’s position relative to the location of buildings reflections (increases in level) and screening effects (reductions in level) can be realized by respective level changes.

Copy the Level’s Time History

The level’s time history can be copied to the clipboard to be pasted into other software (e.g. like MS-Excel or MS-Word), either as sequences of numbers or as a chart.

  • To this end, activate the Level-Time diagram on dialog Pass-by Level by clicking onto it. The upper dialog bar gets highlighted. Now copy to the clipboard by clicking the „Copy“ button (or by pressing the C key).
  • Paste the data into the other software and confirm either graphic or text.

Indicating the vehicle on the road (emission line) by a symbol and in the diagram with a vertical cursor line

  • Check for further options on the Pass-By dialog.
  • Vary the reflection of single buildings by switching them on and off alternately and watching the effect on the level’s time history.

This diagram also facilitates the optimization of barriers, because the effect of a modification can be assessed immediately. Beyond the mere consideration of time-averaged levels, the pass-by feature offers a tool which enables to examine and visualize the effects of level-reducing measures on the actual level.

Video

The pass-by can be recorded as a video using AVI format for replay using any standard video software (such as Windows Media Player). Click the button „Video“ to configure the recording options.

Video Options

  • Section: An existing and named section can be selected which is used for the video output (standard: entire limits). It is useful to define a calculation area within that section.
  • Option „follow source“: With this option activated the video section follows the moving point source.
  • Scale: Upon activation of the entered scale is used, otherwise the scale defined in the project (default value 1:1000).
  • Resolution (dpi): When activated and with a value entered, this resolution is used, otherwise the setting on the main window is used. The larger the value, the finer the resolution and the greater the file size (default value 75 dpi).
  • Frame rate (fps): default value 15 fps

Note

A bitmap used as a background image will not be displayed in the video.

To record a video, a respective compression algorithm (video codec) has to be specified after having entered a file name.After confirming with OK the pass-by is calculated and recorded.