'morse code' like sound thru speakers

Question

Dimension 4100 OS WinXP SP2 Home Edition Speakers harmon/kardon HK - (313-3925)   Recently getting intermittent short bursts of sound similar to morse code sound. Sometimes they will occur twice in quick succession and then long gaps before next time. The volume level of the noise is very low, as if in background. If they occur during a recording operation (eg cassette to pc for later cd burn) the recording is ruined by the distortion. One suggestion has been possibility of sound card going bad. But I don't want to buy a new sound card unless it is indeed the cause. All help greatly appreciated.

Ledswinger · Answer

Most likely cause is interference from a mobile or cell phone's synchronisation signal. Virtually nothing you can do about this, but if it is this it not a system problem, and it won't cause any harm. if you really have an issue, shielded signal and speaker leads might help, but we're talking about a lot of faffing around for minimal benefit.

To check this is what you're hearing, place a mobile/cell phone close to your computer desk, turn the phone on, and turn it off - both events will generate the effect.

Led

fireberd · Answer

RFI, if that is the cause can be coming from the recording source, but I would not expect RFI in the speakers to be feeding back into the systems since the speakers are connected to an output not input on the sound card.    Disconnect the recording source to your PC and then record the line in (I assume that is what you are using) without anything connected and see if you get the beeps.  If there are no beeps then whatever is causing it is being fed in from your source.  First step, make sure you are using a shielded AUDIO cable NOT a 'speaker' or 'headphone' cable which is not shielded to connect the external device to the PC.

lambrusky · Answer

Thanks for the heads-up. It was the cell phone. Took it to another room and heard no further 'noise'. Place it near speakers, turned off and on and duplicated the sound I was hearing. All's well that ends well.

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"morse code" like sound thru speakers

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