Industrial Noise indoors and outdoors with Noise Transmission
The SoundPLAN industrial noise modeling is unique. All questions of frequency dependant noise can be simulated whether it is purely an indoor problem, a receiver outside that needs to be assessed for outside sources, or a complex problem with the source inside an industrial building and a receiver on another building. The simulations inside industrial buildings are completely integrated with the transmission through the outer walls and the propagation into the environment.
Sources for the industrial model can vary between point, line and area sources. The sources can be described with the sound power [Lw] (for a mean frequency, octave or third octave band), with a 2D or 3D directivity and with a time history defining the strength of the source within the 24 hours of the day. Routines to convert sound pressure levels with a given reference distance into sound power and frequency filters are part of the SoundPLAN tools.
For line and area sources, the sound power can be entered for the entire source (as per unit) or as a power per meter/square meter of the source. An excavator in a construction site is a perfect example of a per unit area source. Per meter is a sensible entry for a conveyor belt that emits a certain sound power every meter of its length, whereas the per unit setting would be preferred for a fork lifter with a known sound power that is moving along a defined path.
The industrial building is a core element of the industrial noise modeling suite. This object is used for both indoor and outdoor simulations. Freestanding point, line and area sources are the second object type used to define industrial sources. Both types can be used in combination. Regardless if the indoor noise levels are guessed, measured or simulated, the industrial building is the entry point for the outdoor simulation. In the picture to the left, the industrial building shows sources superimposed on the sides. These are the windows. They are subjected to the same indoor noise levels, but have a different transmission loss. By embedding the sources on the industrial building, SoundPLAN can work with correct spectral sound power and source size information. This is much more transparent than working with differential sources.
SoundPLAN v8 offers a sound particle tracing model. This model allows the consideration of partial walls, the sound transmission through walls and ceilings, the consideration of enclosures, the input and consideration of partial absorptive surface for walls and ceilings.
2D and 3D Directivity
SoundPLAN offers 2 different directivities, the 2D and the 3D directivity. The values are defined every 10 degrees between 10 and 360 degrees. If the values are not entered every 10 degrees, an interpolation allows the values to be evaluated for the directions needed. With the "Norm" button, the directivity values are assessed so the directivity does not scale the sound power up or down.
The 2D directivity comes in 2 variants, the usual horizontal directivity and the rotational symmetrical vertical directivity. The vertical directivity only uses the values in the "eastern" half of the diagram, i.e. the values between 270°-0°- 90°. This vertical directivity is used for smoke stacks and openings that have a rotational symmetry. The rotation axis is always vertical.
The direction 0° of the 2D horizontal directivity is the main direction of the equipment. When digitizing the source, the main direction needs to be set under the "additional" tab of the source definition.
If the directivity is more complex (the source is not only directive in the horizontal plane such as when using loud speakers), a full 3D directivity is available where the directivity is entered for 18 lines of latitude and for 36 values representing the entire "globe" in steps of 10 degrees.