Fluid networks acoustics is a major area of intervention for ITS, the recurring problems encountered being the following:
- noise emissions at the interface between fluid networks and the atmosphere e.g. air inlet and intake, air or fluid, eventually under pressure outlet and discharge (in particular: industrial e.g. exhaust gas, steam, process gas involving thermodynamics and/or chemistry) e.g. exhaust orifice, chimney outlet, decompression (depressurization) vent.
The challenge is then the compatibility of the noise emitted by openings, through which the fluid flows, with constraints which may be of different types (*) (**) (***)
- impact of sound transmission through walls (pipes and conduits, ducts, chimney casing, and other components such as elbows, diffusers, reductions, valves).
The challenge is then the compatibility of the noise transmitted in the half-space that constitutes the exterior of the fluid network (which, for a section, depends not only on the acoustic level inside the fluid network but also on the ability of the wall considered (depending on its nature, geometry, and frequency) to oppose the propagation of sound (its sound reduction is involved), with constraints that may be of different types (*) (**) (** *)
In terms of acoustics of fluid networks, it should be considered that certain components (straight lengths) oppose (a little) the (axial) propagation of sound (by attenuating them, according to their constitution and length), while others are potentially likely to generate very significant noise (valves, changes of section, changes of direction e.g. elbows, bifurcations); the noise transmitted through the walls is therefore all the more important, all other things being equal.
Thus, in relation to fluid networks acoustics, ITS offers services in terms of study (engineering, R&D) (****), sizing of soundproofing materials e.g. duct walls lagging, silencers: resonant and/or absorptive (*****) as well as their marketing, taking into account the particularities of each project:
- pressure vessels: specific calculation codes e.g. CODAP, ASME
- soundproofing devices subject to high physico-chemical constraints: special steels
- silencers with transport of pure hydrogen: lining without binder to avoid the risk of accidental combustion
* e.g. worker protection. In Europe, levels above the limit specified by Directive 2003/10 / EC of February 6, 2003 i.e. daily noise exposure level greater than 80 dB (A) and/or a peak sound pressure level above 135 dB (C), trigger action)
** e.g. preservation of environment (relating to a problem of neighborhood discomfort). In France, an emergence value i.e. a difference between the A-weighted equivalent continuous pressure levels of ambient noise (fluid network in operation) and residual noise (in the absence of noise generated by the fluid network but measured on its period of activity) above certain defined limits constitutes in particular an offense (cf. Environmental Code) - depending on the ambient noise level 5 or 6 dB(A) during the day and 3 or 4 dB(A) in night period -.
*** acoustic comfort in buildings. In some spaces, the equipment noise must not exceed a specified limit: 30 to 50 dB(A) depending on the destination of the room and according to the applicable regulations i.e. decree of June 30, 1999 relating to the acoustic characteristics of residential buildings or decrees of April 25, 2003 relating to noise limitation (health, education, hotels) or according to standards (not of mandatory application) for offices and associated spaces (NF 318080 dated January 2006) or sports halls ( NFP 90207 dated October 1992)
**** measurements, calculations and simulation of internal or external sound propagation - including, with in-house developed software, for the noise emitted by some control valves and gas jets -
***** ITS has developed versatile, reliable and precise acoustic and aerodynamic performance calculation tools and also uses commercial tools: CFD, FEM, BEM