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User-defined Path Geometry

Enter a polygon where each click generates a receiver point within the chain.

Table „Receivers in chain“

At the polygon points of the chain the following parameters are calculated in accordance with the requirements of ISO 3382-3 and VDI guideline 2569:

  • the A-weighted sound pressure level and/or
  • the speech transmission index (STI) referring to a point source assigned,

and the following derived quality criteria:

  • Lp,A,S,4m: A-weighted sound pressure level Lp,A,S at a distance of 4.0 m from the sound source,
  • D2,S: spatial decay rate in dB of the A-weighted sound pressure level Lp,A,S per doubling of distance,
  • rC: shortest distance (m) from the speaker, where the A-weighted sound pressure level is below 45 dB (comfort distance)
  • rD: distance (m) from the speaker at which the speech transmission index STI drops below 0.50 (distraction distance)
  • rP: distance (m) from the speaker at which the speech transmission index STI drops below 0.20 (privacy distance).

Regarding the evaluation of the spatially averaged reverberation times check for Dialog Geometry in this chapter.

Procedure

In order to make use of a receiver chain proceed as follows:

  • Enter a point source with emission data and a height of 1.2 m.
  • Enter a receiver chain as a polygon with multiple points in a row.

Note

The standard ISO 3382-3, a height of 1.2 m of the source and the receiver chain is explicitly required. In CadnaR, receiver chain have a default height of 1.2 m. Other heights, however, may be used. In these cases, a message is displayed.

Note

In order to evaluate the quality criterion D2,S (spatial decay) in accordance with ISO 3382-3, just the points of the receiver chain in the distance range 2 m to 16 m are used. Furthermore, the number of points (measurement positions) in this distance range shall be 6 to 10, but at least four.

  • Select from the dialog Receiver Chain a point source which subsequently will be used as the source location within the calculation of this chain (line "source (PQ)").

After selection of a point source a dashed line is drawn from this source to the first point of the receiver chain to highlight the established link. With several receiver chains in the project, the corresponding point source has to be assigned to each chain individually.

Example

Receiver chain having 7 receiver points and a point source assigned

Configuration

In order to calculate the speech transmission index STI the options „Calculate Echograms and Decay Curves ... for Receivers“ and „Calculate STI/STIPA/CIS“ on the „RIR-Evaluation“ tab have to be activated (see "RIR-Evaluation" tab).

Calculation

The calculation of receiver chain is performed via a separate calculation function, see Calculate Receiver Chains.

Dialog options

Table „Receivers in chain“

A-weighted level and the Speech Transmission Index (STI) depending on the 3D distance from the referenced source.

L_p, A, S, 4m (dB) / D_2, S (dB) / r_C (m) / r_D (m) / r_P (m)

derived quality measures (specification see above)

Path evaluation acc. to VDI 2569

  • display of the „Propagation Class“ (class 1 "favorable" to 3 "unfavorable") also checking for the criteria for D2, S and Lp, A, S, 4 m acc. to Table 9, VDI 2569. If the variable GanzzahlKG=1 is set in the memo field of the receiver chain, the determination of the „Propagation Class“ is based on the rounded integer values of D2,S and Lp,A,S,4m. Using GanzzahlKG=2, the values are also displayed as integer values in the dialog.
  • display of „Room Acoustics Class“ acc. to Table 11, VDI 2569, being fulfilled by the calculated reverberation time T20 (class "A" favorable, class "C" unfavorable). With several receiver chains present, the worst RA-class of all IP-chains is displayed.The details of the analysis are listed by selecting the command Evaluate Receiver Chains on the Options menu (see Evaluation Receiver Chains).

Result Table spectral

The spectral table shows the spectral room acoustical parameters T30, T20, T10 and EDT - when selected for calculation - averaged for all receivers in the receiver chain (see "RIR-Evaluation" tab).

Note

Besides displaying the results (per variant, if any) on the dialog Receiver Chain they are also written into variant-specific attributes which can be addressed. In order to access an attribute the variant number gets attached, e.g. LPV03 to access the A-weighted level of the 3rd variant, EDT_2000V05 to access the Early Decay Time at 2 kHz of the 5th variant etc. With no variant number attached the value of the actual variant gets accessed (see Object Attributes).

Consistency Check

Prior to the calculation of receiver chains CadnaR performs a consistency check with respect to the following criteria:

  • height of all the receivers in all receiver chains and of the referenced point source/s not at 1.2 m,
  • no point source assigned to receiver chain/s,
  • too few valid polygon points (at least 4, 2 m minimum distance from the source),
  • frequency range for STI calculation incomplete (required 125 to 8000 Hz, see "General" tab): In this case, the calculated STI value is displayed in square brackets („[...]“).

If a single or more of the criteria are met, a dialog is displayed enabling to access to the relevant objects to change settings. In order to proceed with the calculation despite violated criteria click the „Continue“ button.

Dialog Geometry

Dialog Level Diagram

Level Diagram: shows the A-weighted sound pressure level Lp,A,S at all points of the receiver chain as a function of the 3D distance (m) from the sound source, and the regression line in the distance range from 2 m to 16 m (also displaying the numerical values for Lp,A,S,4 m, D2,S und rC)The points of the receiver chain in the distance range from 2 m to 16 m, used to determine the regression line (red) are filled black, while those outside the range are filled white.

STI diagram: shows the speech transmission index STI as a function of the 3D distance from the sound source (with displaying lines of rD (distraction distance) and rp (privacy distance).The regression line results all points of the receiver chain (and not just from the distance range from 2 m to 16 m).

DialogReverberation time

Reverberation Times: shows the spatially averaged reverberation times T30, T20, T10 or EDT for all receivers of the receiver chain (by default: T20) depending on frequency. Additional settings and descriptions of the menus, see Spatially averaged reverberation time (Receivers + grid).