The noise, if it is a 50Hz hum, likely is caused by a groundloop due to the electrical wiring. It is typical for (many) laptops. The only reliable way is to insert a groundloopadapter. Check your audio store. Should not have to cost more than like €10,- (else check another shop)
looks like this
http://www.new-line.nl/nl/di-box-stagec ... _12698.htm (sorry if you do not understand the Dutch part)
The adapter should be as close to the source (but after) as possible; if you use dual setup, consider buying at least 2.
I always take these with me and use them if I hear the slightest hum. (typical sources are dimmers, lighttubes, microwave, industrial dishwashers in restaurants). And last but not least when connecting a MP3 like device headphone to car AUX, where sometimes the noise is synced with the engine's RPM...
