Air, exhaust / combustion gases, steam and all industrial fluids: all silencers (sound attenuators aka mufflers) are studied and / or marketed by ITS.
With respect to aeraulic networks (e.g. ventilation, air conditioning) or to networks of fluids being pressurized (in particular: industrial e.g. water vapor, oxygen, nitrogen, natural gas) or at a pressure nearly atmospheric (as for many industrial chimneys):
- it is often a question of attenuating the noise transmitted by openings, at the upstream end (air intakes and inlets, suctions holes, e.g. of combustion air) or downstream (discharge, outlet of chimney, decompression vent): the reduction in the sound power level transmitted by them is in this case directly linked to the insertion of a silencer (sound attenuator aka muffler)
- it is sometimes a question of limiting, at specified locations, the transmission of noise through walls of ducts, conduits, pipes: reduction (on the path of sound waves from the noise source to such locations) the sound power level inside these network elements which carry the noise allows, all other things being equal (and in particular: for a noise reduction of the walls being constant) to limit the sound transmission towards the outside
Depending on the context, the noise source whose impact must be mitigated can vary (from one project to another, or: partially, coexisting with others e.g. in the case of power plants), being possibly:
- a fan: not only considered individually or as a component of various Heating and Ventilation Air Conditioning (HVAC) equipment in buildings, but also, for industrial applications (e.g. draft fan, air condenser, cooling tower)
- a compressor
- a heat engine
- a combustion turbine
- a control valve
The discharge to the atmosphere of pressurized gas (e.g. emptying of tanks, activation of safety valves, decompression of all kinds) does not involve any material constituting in itself a noise source, but is nevertheless, intrinsically, a very noisy oeration often requiring the implementation of silencers (sound attenuators aka mufflers).
In terms of study, for what ITS has advanced (if not outstanding ?) human and material resources, with simulation software developed in-house and also with tools from other specialized editors e.g. CFD, FEM, BEM:
- simultaneous consideration of an acoustic performance objective (insertion loss in dynamic regime, a fortiori when it is desired that it is high) and an aerodynamic performance objective (total pressure loss, a fortiori when it is desired that it is low), which are, by nature antagonistic, often makes iterative (sometimes: tedious) calculations necessary to find a technically satisfactory compromise; this situation can be complicated if additional technical constraints are taken into account e.g. a limitation of the speed of the fluid in the air channels of the silencer (sound attenuator aka muffler), a limited space for the soundproofing device
- taking into account very high speeds (as at the exhaust of very large gas turbines but also downstream of - smaller - regulating valves or jets orifices) complicates the calculations, whether in relation to the propagation modes of the sound in the porous media constituting the lining of the silencers (sound attenuators aka mufflers) and in the transported fluid, or whether it is due to the flow noise (self noise) thus created, such as to degrade, in dynamic regime, the performance of any silencer (sound attenuator aka muffler) when compared to static regime
- the consideration of very high temperatures as in the exhaust of heat engines or combustion turbines or the consideration of very high pressures as in the case of pressurized fluids, requires, before anything else, to predict (by appropriate modeling) the acoustic behavior of sound absorbing lining materials, whose measurements of characteristics in the laboratory (i.e. at ambient temperature and pressure) do not account for such different thermodynamic conditions
- moreover, taking into account other parameters can influence the design of silencers (sound attenuators aka mufflers), in particular the choice of packing materials with regard to the risks of corrosion and (in general) of deterioration e.g. the content in humidity or in corrosive effluents (namely in case of the the presence of acids in fumes) of the transported fluid, or with regard to fire risks e.g. in case of the possible presence of pure oxygen
Time has no equal to allow you to familiarize yourself, depending on the projects, with the different aspects of the very specific engineering work that constitutes the design of a silencer (sound attenuator aka muffler), whatever the fluid to be considered (air, gas exhaust / combustion, steam and all industrial fluids); to supplement the general information, related to sizing, reported above, the following one can report:
- the silencers (sound attenuators aka mufflers) for ventilation or air conditioning networks are of an ordinary technical level (in terms of dimensioning, a recurring difficulty is, nevertheless, often the need to have, at low frequency, a significant performance with a limited space requirement)
- silencers (sound attenuators aka mufflers) for fluids under pressure involve complex phenomena in terms of acoustics and in terms of fluid mechanics: sophisticated calculations are required in this area, to be completed by mechanical resistance calculations, as for other pressure vessels
Meanwhile, construction, according to modalities guaranteeing delivery deadlines, quality, durability of the silencers (sound attenuators aka mufflers) marketed by ITS is in line.