SoundPLAN Application - Indoor Noise Model

The SoundPLAN Indoor Noise Model is based on the German VDI 3760   "Computation and measurement of sound propagation in workrooms", published 1994. 

The VDI 3760 standard makes the following assumptions:

1. The laws of geometrical acoustics hold; wave phenomena are absent.
2. Surfaces, which are all planar, reflect the sound energy spectrally as if from an infinite plane.
3. Sound is treated as an energy function, not as a pressure function. Thus energies may be summed directly and phase effects are absent.
4. Surfaces absorb sound energy according to an energy absorption coefficient which is independent of the angle of incidence.

(Note: Interested in the Indoor Calculation Method -> Calculation Equations)

The SoundPLAN Indoor Noise Module uses a ray tracing algorithm that scans the geometry in the x-y plane. The third dimension (z-direction) is considered by creating mirror sources based on the plane and horizontal floor and ceiling geometry. This model allows modeling of buildings and rooms with arbitrary floor plans, but flat and parallel floors and ceilings.  The definition of source includes point, line and area source.  The source can be defined with 1/1 octave band or 1/3 octave band spectra.

Several calculation types are available for the Indoor Noise Model:

• Single Point Receivers - Calculation for specific receptor location
• Sound Decay Curves - the acoustical room transfer function is computed over a propagation path
• Grid Noise Map - calculation over a grid area to generate noise contour maps

The 4 JPG file below show a sample project generated with SoundPLAN Wins. 

The data shows a room with five sources [Sound Power Level each Lw = 105 dB(A)].   The room height is 4 m.  The walls, floor and ceiling are reflective (i.e. concrete).  A high density of scattering objects (tables, shelves, racks, etc.) was considered throughout the room. Two models were computed, one without any interior walls, and with interior walls (absorptive surface). 

1)    Analysis Map w/o Interior Walls

Map shows the noise distribution throughout the room. 

2)    Prognosis Map w/ Interior Walls 

The noise contour map shows the influence of the interior walls in respect of absorption and shielding. 

3)    Difference Map (w/o vs. w/ Interior Walls)

The Difference Maps visualizes an change in noise level in the near field of each source, close to the interior walls and the reduction due to the interior walls in the center of the room.

 

4)    3D Noise Contour Map Prognosis Map w/ Interior Walls

The graphic visualizes the predicted noise levels with the interior walls in reference to the room geometry.

5)    Sound Decay Curve

The spectral sound decay graphic presents the acoustical transfer function on a straight path through the room.  The graph shows the difference in noise transfer between the low, mid and high frequencies in reference to an outdoor free field propagation (6 dB/DD).  Effects such as reflective surfaces, The 

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Other Calculation Run include other Room Modifications:

• Acoustical Ceiling Treatment
• Acoustical Treatment of Exterior Walls
• Noise Enclosure for Sources.