QSI - Statistical Analysis
The „Requirements and Testing Conditions for statistical qualification of level differences“ stated in DIN 45687 45687-2006, annex F (available in German only) are implemented in CadnaA. To statistically evaluate the level differences from two calculation runs with different configuration settings the 0.1-quantile and the 0.9-quantile are calculated and displayed (10%- resp. 90%-value of the distribution of the level differences).
The command QSI-Statistical Analysis is available via the menu Tables |Miscellaneous. The evaluation may be applied to grid points, to facade points or to points on lines of equal sound level (Iso-Lines).
Dialog QSI - Statistical Analysis
The statistical evaluation in CadnaA considers all active receiver points (minimum number of receivers = 20). The additional requirement according to annex F of DIN 45687 regarding a minimum horizontal distance of user-defined receivers of 2 m from sources and obstacles has to be ensured by the user himself. When receivers are generated by CadnaA the minimum horizontal distance will be respected automatically.
Assignment of Variants
Specify which of the variants in the project file should be considered as reference configuration and as project configuration. Normally, the setting „(default“)“ applies for the reference configuration which is defined globally (see below, Reference Configuration). With the default reference configuration selected, the additional variant „REF“ (corresponding with variant V16) will be listed on the list boxes „Reference Configuration“ and „Project Configuration“ after calculation.
Reference Configuration
As far as the reference configuration is concerned the default values (setting „Default“) can be applied or be altered by the user (setting „User defined“). In the latter case the default reference configuration values will be listed in the box upon click onto the button „Copy Default“. The parameters listed in the table below are available for the time being..
| parameter (unit / value range) | variable/default value |
| maximum error (dB) | MAXERROR=0.0 |
| search radius (m) | SEARCHRAD=3000 |
| grid interpolation on/off (1/0) | RASTER_INT=0 |
| raster factor (-) | RASTERFACT=0.5 |
| projection of line sources on/off (1/0) | PROJ_LQ=1 |
| projection of area sources /off (1/0) | PROJ_FQ=1 |
| order of reflection (1-20) | REFLORDER=1 |
| max. distance source-receiver (m) | REFL_DMAX=3000 |
| ibid, interpolate from (m) | REFL_DMAXI=3000 |
| reflector-search radius source (m) | REFL_RAD_S=3000 |
| reflector-search radius receiver (m) | REFL_RAD_R=3000 |
The reference configuration settings can be changed by entering different values for the parameters as required.
Evaluation Parameter
Select the evaluation parameter used for the statistical evaluation. With setting „(current)“ the active performance parameter is used.
Test Points
DIN 45687, annex F, requires a minimum number of 20 receivers for the evaluation.
use existing Receivers
In order to use the existing receivers shall, their ID must be changed to the text string „QSI“ in order to be considered upon calculation.
generate new Receivers
By activating the option „generate new Receivers“ three options are available:
- Grid Points: By clicking the „Calculate“ button the specified number of receivers will be generated at arbitrary locations. With a calculation area defined the receiver points will be distributed inside that area, otherwise within the entire limits.
- Facade Points: By clicking „Calculate“ the specified number of facade points (as QSI-receivers) will be generated at arbitrary locations (at a distance off the facades specified on dialog Building Noise Map). The generation of facade receivers requires to generate building evaluation symbols for a reasonable number of buildings in the project (or for all buildings). Facade receivers will just be generated for buildings having a building evaluation symbol addressed.
- Points on Iso-Lines: With this option the approach is different. First, select on dialog Configuration of Calculation the project configuration as required and recalculate the grid (via Grid menu). Now, select on dialog QSI-Statistical Analysis the option „Points on Iso-Lines“ and change - if required - the reference configuration. By clicking „Calculate“ the specified number of receiver will be generated at arbitrary locations on the iso-line with the specified level. This option requires that a valid grid exists. The appearance of the grid is not relevant.
Calculation of Test Points
This option enables to control whether the reference and/or the project configuration should be considered upon recalculation. In case of evaluation options „Grid Points“ and „Facade Points“ the settings of the project configuration can be altered directly via the file-selector symbol.
Results
This box displays the results of the statistical evaluation, as there are:
| resulting parameters | abbreviation |
| 0,1-quantile | q0.1 |
| 0,9-quantile | q0.9 |
| standard deviation of level differences | sigma |
| mean value of level differences | mean |
| minimum level difference | min |
| maximum level difference | max |
Individual Results
The lower table displays the coordinates of the receiver points, the levels for the reference and then project configuration, and the level differences.
Word-Export
Upon click on the button „--> Word“ both configuration settings, the results for the statistical parameters, and the individual results will be exported to MS-Word. The template file QSI_TMPL.RTF supplied with CadnaA (see installation directory) can be edited by the user.
In section „Configuration“ only those parameters are displayed where the reference and the project configuration differ from each other. At the end of a QSI-analysis, this enables to check whether the intended settings for both configurations have been set correctly.
Example
The influence of the projection of line sources on the receiver level shall be statistically be evaluated for a project with roads and buildings. The receiver points for QSI-analysis will be generated by CadnaA. In the reference configuration, the projection of line and area sources shall be turned off and the maximum error shall be set to 1 dB.
Open the QSI-dialog an assign the variant „(default)“ for the reference and V01 for the project configuration. To check for the default-reference settings switch to „User defined“ and click the button „Copy default“ to display all relevant parameters. The project configuration shall comply with this reference configuration, besides the projection for line sources deactivated.
To check and alter the project configuration, click on the file-selector symbol in the dialog section „Calculation of Test Points“. Ensure that the projection of line and area sources on tab „Partition“ is deactivated and enter on tab „General“ a maximum error of 1 dB.
Run the calculation with options „Test Points, generate new Receivers, 20 Grid Points“. The result is displayed below.
QSI-result after calculation
The exported MS-Word-file indicates that the project configuration differs from the reference configuration just by the setting of projection of line sources (template file QSI_TMPL.RTF edited).
