Beating/Ticking sound problem

[#1]

Hello,

My Xperia Ray (running ICS) is a perfect phone exept for one thing:

When I connect the phone to external speakers, a strange heart-beating sound appears which is followed by ticking sounds, like a metronome.

If I connect the phone while the music player is on and playing a song, no beating/clicking occurs.

Airplane mode seems to fix this problem, though.

Any comments/help would be appreciated.

[#2]

That sounds like the phone polling for the network occasionally. Its normal.

[#3]

My friend's phone, ZTE Blade, is on the same network and is not emitting these noises, which are actually annoying. Is there a way to somehow silence them down?

[#4]

My guess is the Blade isn't polling the network as normal.  Move the phone further away from the speakers if possible, its EMI between the radio in the phone and the speaker mechanism