Nozzles [1] are components which are often present in duct systems such as those to be envisaged for air conditioning systems, ventilation systems for premises or for enclosures (in general: each time the installation of a fan is to be envisaged), exhaust lines for thermal engines or gas turbines, etc ...

The acoustic performance of nozzles must be accounted for the purpose of the design of equipments for which noise transmission at extremities of the duct systems must be limited, being a reduction in the sound power level which is important e.g. when it comes to predicting the sound level in specified locations (inside premises e.g. at the level of the outlets of an aeraulic network or outdoors e.g. at the outlet of a chimney).

ITS has integrated the prediction of the acoustic performance of nozzles to the simulation software SILDIS®.

Calculation routines have been implemented for the calculation of the insertion loss (attenuation) of those equipments (with a rectangular or a circular cross section), the main input data taken into account for modeling the acoustic performance of ducts being as follows:

  • the characteristic dimension of the duct
  • the physical parameters (according to the thermodynamic conditions) of the transported fluid, impacting sound speed
  • the solid angle factor (varying depending on the number of sound-reflecting planes near the considered nozzle)

Following the modification operations of the software SILDIS®, the comparison of simulation results with bibliographic data (results of measurements, results of calculations by others ...) has shown a satisfactory agreement for the noise transmission of nozzles with various geometries and dimensions.

The expected result of improvements to the acoustics calculation software SILDIS® (for the prediction of the acoustic performance of nozzles)is an improvement of the accuracy of the definition of the performance required for soundproofing equipments such as ventilation silencers and in general: of all industrial silencers (and of their connecting parts) which design is very demanding given the sound power levels of the considered noise sources (before soundproofing) and expected performance in terms of sound insulation in the context of protection of workers, or of preservation of environment, or of improvement of the acoustic comfort in buildings.

[1] ends of aeraulic networks e.g. Heating Ventilation Air conditioning (HVAC), air inlets, burnt gas or pressurized fluid exhausts