Why Does My Computer Speaker Make a Clicking Noise?

[LENIN]

Why do some computere speakers make a loud clicking noise whene they are turned on after a long time? I noticed this hapening with my speakers, but only if theye where sjut down for a while. If I just turn theme off and on agein I don't heare the clicking noise. Wht is these noice. My first gues would be it has something to do with a capacitator but I would be really glad if someon could explain what it is. Thanks!

 

[berkeman]

The speaker element is a coil around a magnet. When current is driven into the coil one way or the other, that moves the coil, which is connected to the cone of the speaker, and that generates sounds. When the audio amp that drives the speaker is powered up and just sitting there, the output of the amp is at about half of the power supply voltage of the amp, and there is a capacitor between that output and the coil to isolate that DC voltage from the inductance of the coil. The quiescent voltage across the coil to ground is zero.

When the audio amp is off, the voltage at its output is zero, and the capacitor has zero voltage across it. So when the amp is powered on, the audio amp side of the capacitor gets pulled up to half of the power supply voltage, and that transient can often be heard as a pop sound in the speaker. The harsher the power-on transient at the output of the audio amp, the louder the transient will be at the speaker. Good audio amps are designed to minimize the power-on transient rate.

 

[LENIN]

Thanks berkeman!