Silencers in Home Cinema Air Conditioning Systems - November 9th, 2008
The noise generated by air/gas handling equipment, such as fans in an air conditioning system of a home cinema, is controlled through the use of two types of devices:
1. Passive silencers and lined ducts whose performance is function of the geometric and sound-absorbing properties of their components and
2. Active noise control silencers whose noise cancellation features are controlled by various electromechanical feed-forward and feedback techniques.
We will focus on passive silencers for now, because they are widely designed and used in dedicated home cinema installations for noise control.
For a start, the term ’silencer’ is often used generically to refer to any type of passive noise control device. The majority of noise sources like an air conditioning system in a home cinema system, has an intake and an exhaust and, generally, it requires both intake and exhaust silencers. The two cases are characterised by different flow direction, back pressure, average gas temperature, and average sound pressure levels, but the corresponding hardware is developed using the same principles and design methods.
The use of a silencer in a home cinema installation is prompted by the need to reduce the radiated noise of the air conditioning system but, in most applications, the final selection is based on trade-offs between the predicted acoustical performance, mechanical performance, volume/weight, and cost of the resulting system.
Most silencers in dedicated home cinemas are subject to size constraint, which also influence the silencer design process. In addition, home cinema designers need to consider the initial purchase/installation cost and the periodic maintenance cost; these are all factors that will influence the silencer selection process for the home cinema room. Since noise is the root cause of silencer design in hi-end home cinema installations, the acoustic engineer needs to be able to predict its acoustical performance and back pressure.
One can of course purchase generic pre-built silencers, if a custom design is not a possibility.