"mic in" jack audio problems...

Discussion in 'Laptop Hardware' started by ankhaw93, Sep 16, 2008.

  1. ankhaw93


    Sep 16, 2008
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    When using the "mic in" jack I'm getting a noise. It only happens when I have a cord plugged into the mic in jack, and it happens to any cord I plug in, regardless of if I have a microphone plugged into the cord or not. The noise is a somewhat rythmic hum, repeating everyone 1.25 seconds, approximately.

    I'm an audio engineer for radio broadcast, and I intend to use my Aspire One to record and playback audio, using the program Audacity. I've tried plugging in different microphones, cords, and audio sources, and I consistently get the noise. I've then tried some of the same cords and audio sources on another computer and NOT gotten the noise. I've also recorded some audio using the built-in microphone on the aspire one and NOT gotten the noise, so it seems to be only on the mic in jack on my new computer. The noise is directly affected by the volume setting on the recording section of the sound software on the computer... the louder the recording level is set, the louder the noise is, of course.

    I have an MP3 recording of the noise, if anyone wants to hear it and help me diagnose...

    Forgive how long this post is, but I wanted whoever reads this to know that while I'm not a computer expert, I AM very good with audio, and troubleshooting audio problems, and after checking and doublechecking and triplechecking, whatever problem is happening is centered on the "mic in" jack on the computer, not with any other audio source, cable, or my recording software.

    So, has this happened to anyone else?

    ankhaw93, Sep 16, 2008
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  2. ankhaw93


    Sep 21, 2008
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    I know exactly what buzzing you are referring to! My Aspire One with Windows Xp had the exact same problem. I, like you, tried various mic & headphone combinations (even tried USB mics!) but nothing got rid of the buzz. Well, today I updated the BIOS to version 3304 (from 3114) and it seems to have removed the loud buzzing while recording with Audacity. So, you might try updating your BIOS. There are several postings on this bulletinboard that will tell you how to do it. I have a link that will give you a sample of what a recording sounds like after a BIOS update.


    Hopes this helps! :)
    Raytown, Sep 21, 2008
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  3. ankhaw93


    Sep 21, 2008
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    Same audio problems at mic-in for my AA1 -1GB-120GB HHD- XP home when using Audacity.

    My findings:
    1) The mic-in jack is for a stereo mic. Mono PC mic should not be used.
    2) There is 2.5 Vdc bias at L and R channels (for active capacitance stereo mic ?).
    3) Capacitors (say 1uF) should be used at both channels to block the bias DC if it is to be used a stereo line in.
    4) A signal generator was used to test the recording frequency response from this input. It is from 30 Hz to 8.5kHz. The roll-off is very steep after 8.5 kHz. It seems that digital filtering is used. The recorded signal phase is inverted.
    5) The audio noises at the recorded signals at both channels are quite high and don't think that it is good for recording purpose. These noises could be caused by the WiFi card because it is too near the mic in jack.
    6) Testing WAVE files were used to test the play back frequency response at the ear-phone output. It is flat from 30Hz to 16kHz (-3dB at 20kHz) when observed in CRO. The output phase is inverted with maximum output voltage of 3.5 V peak to peak.
    7) The playback from good audio (wave and MP3) files is very good.

    Some suggestions:
    Maybe an external line-in to USB convertor could solve the problem?
    The7, Sep 21, 2008
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