Laptops and phone lines

[#1]

An acquaintance has suffered from a noisy line,and having done all the tests was about to report to his ISP.
However his son, who used a wifi connected laptop had to go away. Now the noise has vanished.
Is it just coincidence, or could the laptop be a cause of the noise? If 'yes', what could be the problem?

[#2]

First suspect might be a faulty PSU.

[#3]

Electrical  devices can cause problems to your connection as mentioned above.
See here for a better explanation than I can give.
http://www.kitz.co.uk/adsl/rein.htm ;
Can be hard to track down at times.

[#4]

thx guys
btw how easy is a PSU to test?

[#5]

Not easy to properly test as you need some serious spectrum analyser kit and a Faraday cage.
However, if you unplug the laptop and run it on batteries and the issue goes away then you can probably narrow it down to the mains power brick. This is especially true if its an aftermarket one rather than the original .....