|Your speaker is most likely blown. Yes laptop speakers can blow, if you pump enough distorted, heavy bass, music through them they will blow. |
Other then that, they dry rotted or have corrosion on the voice coils.
Other then that, there is something loose, the transistors are picking up noise, the transistors is failing, there is noise in your AC line. Your audio drivers are wrong/corrupted, there is a cell phone interfering, your volume knob, or potentiometer is failing, you have broken your head phone jack, you microphone is adding feedback to the system.
That's all I can think of now,
But I know there is much more.
Please leave your make / model of your computer, what had happened up to this point and what you have tried to do to troubleshoot the problem.