請問我打電話時...點解電腦個揚聲器.會發出拆聲..

I presume that you are using a mobile hpone or a cordless phone, but not a fixed-line one.

When a mobile phone or cordless phone is in operation, there is a continuous transmission and reception of elctromagnetic waves by the phone. The electric field and magnetic field intensities close to the phone is usally quite strong. For common moving coil loudspeakers, there a coil inside. When you place the phone near the loudspeaker, the time varying magnetic field emitted from the phone causes induced current in the loudspeaker coil. This induced current disturbs the oscillating movement of the coil and is heard as some unusual noices.

我都好有興趣知
買speaker時個sales話我個speaker防磁的
但買番黎咪又係會dd沙沙聲....

聽收音機時,有來電的話都會有咁的聲的~
唔知係個收音機發出定係我個earphone發出的~