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Displaying Sound Rays

When the option „Generate Rays“ is activated in the dialog Receiver all calculated rays with this target point are inserted as auxiliary polygon lines. With double-click on such a ray its contribution to the sound level at the receiver is indicated. This sound contribution is shown in the field „ID“ with its proportionate level, e.g., RAY_419_00 which signifies that the direct sound ray (_00) contributes 41.9 dB.

The rays are shown on screen as if they cross screening objects straightly - nevertheless screening is calculated taking into account vertical and lateral diffraction. In this case an s will be attached in their identifier. A shielded ray of the eighth order for which a calculation of diffraction has been enforced may have an identifier RAY_419_08s.

Due to this, rays with a certain order of reflection can be displayed or switched off easily in CadnaA with the efficient group function (menu Tables|Groups see Groups). If the rays are displayed, all diffracted sound rays can be switched off in the representation by deactivating the group with the expression match(ID$, "*_??S").

With corresponding settings for all deactivated objects in Options| Appearance (see Object Appearance) you can enforce the diffracted and non-contributed, mostly irrelevant rays to disappear completely.

Example

  • Start CadnaA
  • In Options|Limits enter the values for the limit as shown in the following dialog.

Insert the following objects

  • Point source with PWL 100 dB, Name Q1 - coordinates 20/5/5
  • 2 buildings with a height of 25 m and Reflection loss of 0 dB:- building 1 (80/60, 85/60, 85/100, 80/100)- building 2 (0/130, 5/130, 5/160, 0/160)
  • Click in the toolbox on the icon and enter the value 80 via the keyboard - hereby an edit dialog opens to enter a polygon point - press the TAB key and enter the value 60 - confirm with OK and enter the next value for the second pair of coordinates.
  • After inserting the coordinates of the first building, quit the insertion mode by clicking with the right mouse button.
  • Again with the right mouse button, click once on the line of the building plan - the edit dialog opens.
  • Click on the button „Geometry“ and enter a building with a relative height of 25 m.
  • Repeat this for the second building. The building height is adjusted automatically.
  • 2 Receiver points:I2 (35/110/5) andI3 (35/170/5)
  • Click on the corresponding icon in the toolbox
  • Enter the coordinate via keyboard and close the edit dialog Polygon Point by clicking OK.
  • Open the edit dialog by clicking with the Right mouse key on the margin of the receiver point.
  • Confirm with OK.
  • In Calculation|Configuration|Reflection adjust a maximum reflection order of 2 or more.

The rays for the receiver R3 shall be displayed.

  • In the edit mode, open the edit dialog for receiver I3 by double-clicking on its border and activating the option „Generate Rays“.

  • Now start the calculation with a click on the Pocket Calculator symbol on the symbol bar.

The following representation occurs after the calculation. CadnaA has calculated the direct ray, a reflection of the first order and a reflection of the second order. CadnaA calculates reflections completely up to the specified order.

situation after calculation and display of rays

After double-clicking a ray - or by Tables|Other Objects|Aux.Polygon - you can identify the rays on the basis of its ID, e.g., RAY_419_00 which means that the level contribution of this ray is 41.9 dB and the last two digits indicate the order of reflection. Double zero is the direct ray without reflection, 01 is a reflection of the first order, 02 of the second order and so on.

Note

Note the possibility in CadnaA in the tables - if you click on a data record, e.g., of the table Other Objects|Aux. Polygon the corresponding ray in the diagram will be marked and can easily be identified.

Now, only rays of the 2nd order shall be displayed. This is achieved not by directly switching those rays off, but by using a suitable group definition.

  • Insert in the Group table on the Tables menu a new row (press the INS key, or select Insert command from the table‘s context menu).
  • Double-click into the row, edit the name and enter the expression „*_02“ and close with OK.

  • Insert a second line after the first one and enter the expression „ray*“

  • Deactivate this group by entering a minus sign in column „Variant V01“.

After confirming with OK just the rays of second order are displayed.