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Reference Time Tab

Reference Times and Penalties

The reference time specifies the time interval for the calculation of the average sound pressure level considering the actual operating time of the source with respect to the basic evaluation requirements.

The specification of a reference period is always required when the emission from different periods Day/Evening (Recreation Time)/Night D/E/N shall be combined to a mixed evaluation level (e.g. Lden, Lde).

In general, penalties for noise-sensitive daily periods are used to account for the increased noise effect (annoyance) when calculating such mixed evaluation levels.

Dialog options

Allocation Hours - Periods

On the upper part of the „Reference Time“ tab the 24 daily hours are allocated to the periods. Each hour can be assigned to one of the daily periods Day/Evening (Recreation Time)/Night by entering a letter (D, E or N, uppercase or lowercase).

This flexible concept enables to meet all the requirements of the EC Environmental Noise Directive (also when possibly shortening the Night period and the lengthening the Day and/or Night period).

If individual hours are not to be taken into account, the relevant box can be left blank (see examples below).

The reference periods defined apply to all noise types and affect the mixed evaluation levels such Lden and Lde (see Evaluation Parameters Tab). For the non-mixed evaluation levels (such as Ld, Le and Ln) no time correction and no penalty is considered.

The following rules apply depending on the different noise types:

  • industrial sources: The reference periods will be considered only when on the source dialog the option „Operating Time (min)“ has been selected with operating times specified or when diurnal pattern has been selected (see Common Input Data).
  • road: Depending on the selected calculation standard the receiving level is just calculated for day and night only. In order to perform calculations involving the allocation of hours (e.g. for the EC Environmental Noise Directive) diurnal patterns for roads have to be used - if the selected road noise standard does not provide traffic volumes for the periods D/E/N distinctively (see Roads, for each road standard, and chapter Road Tab).
  • railroad: as with road, applying the option „Use Non-Standard Reference Time D/E/N“ (see Railways, for railway standard, and chapter Railroad Tab).
  • aircraft noise: see railroad (for „Aircraft Noise“ tab see manual FLG)

Note

The calculation of the noise indicators Lden and Ln according to the EC Environmental Noise Directive is possible with the standard version of CadnaA. By contrast, the evaluation of noise levels statistics with respect to the number of exposed inhabitants requires the evaluation method „Object-Scan“.

Penalties

Penalties are only taken into account for mixed evaluation parameters, such as Lden or Lde. Enter the required penalties according to the applying legal requirements. For example, according to the definition of Lden enter penalties for the period „Evening/Recr. Time Penalty“ of 5 dB and for the period „Night“ of 10 dB.

Recreation Time Penalty only for

Note

This option refers the a specific part of German legislation requiring to apply the recreation time penalty only to „general“ and „pure“ residential areas, but not for mixed or industrial areas. In contrary, this option is on most or all other countries no required and has to be deactivated.

If this option is activated, select the types of land use for which recreation time penalty shall be considered. This selection requires that

  • objects „Area of designated Land Use“ have been entered in the project and a type of land use therein has been selected, or
  • receivers have been entered with a type of land use assigned.

Examples for Reference Times & Penalties

No Settings on „Reference Time“ tab Remarks
1 plus: land use type specific recreation time penalty activated To consider the loudest hour during the night only one letter N is entered in the allocation of hours. In this case, the operation time entered during the night is the operating time (min) of the source during this single hour.
For the periods „Day“ and „Evening/Recreation Time“ the operating time refers to the reference times 13 h D (= 960 min) and 3 h E (= 180 min).
The penalty for „Evening/Recreation Time“ is 6 dB. The surcharge 10 dB for Night is irrelevant since there is mixed level be used combining the night period; the evaluation parameters are Lde and Ln.
2 Alternatively, in order to determine the loudest hour during the night, the letter N is entered for all hours of the night and the evaluation parameter L1hMaxN is selected (see Evaluation Parameters Tab).
This requires, however, that for each relevant industrial source a specific diurnal pattern is defined and addressed via the source‘s dialog.
The further settings are as for No.1; the evaluation parameters are Lde and L1hMaxN.
3 In order to perform calculations according to the EC Environmental Noise Directive the following allocation of hours is assumed: 12 h D (starting at 6 o‘clock), 4 h E (starting at 18 o‘clock) and 8 h N (starting at 22 o‘clock).
The penalties are 5 dB for „Evening (Recreation Time)“ and 10 dB for „Night“.
Both penalties are relevant when calculating the day-evening-night noise index Lden, not however, for the night-time noise index Ln.
4 similar to No. 3, but the Day period has been extended to 14 hours (from 6 to 20 o‘clock).
The extended Day period does not receive a penalty when calculating Lden.
The shortening of the Evening period by 2 hours and the corresponding lengthening of the Day period corresponds with the provisions of the EC Environmental Noise Directive (EU2002/49/EG-2002, Annex I).
In case source-specific operating times are used, those - as before - refer to the above mentioned periods.
5 The allocation of hours just uses the letters D and N. Thus, an Evening period does not exist.
The mixed level Ldn is assessed by adding a penalty of 10 dB for „Night“. Further, the Night level Ln calculated.
The specified penalty for „Evening/Recreation Time“ of 5 dB is irrelevant.

Adjusting the configuration

Regarding the option „Special Reference Times for Industry (min)“ on the „Reference Time“ tab of former releases of CadnaA see Adjustment of the Configuration.