The unbelievably rapid advance in electronic devices has led to some challenging problems for all manufactures of hi-fi and home cinema equipment. Twenty years ago it would be would have been questionable that the combination shield described above would have offered any real benefit.

There are now numerous sources of interference in every household. Mobile phone chargers, switch mode power supplies and energy efficient lighting can all have a seriously detrimental effect, not just on the sound of hi-fi but also on the picture quality of a home cinema system. High frequency interference isn't necessarily airborne; the mains supply is also likely to be extremely polluted. To gain some idea of just how badly this can affect sound and picture quality try this. Play a piece of music or section of film then disconnect every appliance in the house you can get away switching off and play the same piece again. The results can border on astonishing. We were lucky in discovering just how badly this type of interference will affect a system's performance very early on, and developing effective shields has been a major part of our design programme for some years.

http://www.ofcom.org.uk/static/archive/ra/topics/research/RAwebPages/Radiocomms/pages/interexpl/houseapp.htm

http://www.tiresias.org/guidelines/household_appliances.htm

http://www.davidicke.com/forum/showthread.php?p=253283