Audio Feedback – Where To Troubleshoot?

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We occasionally get a sort of feedback/echo noise on our phones here. (Polycom IP550 / Asterisk 1.8). It lasts for about a second, and it’s described by users as ‘jingle bells’. It happens when people are using the speakerphone, especially when it’s on both ends. It happens on internal calls, so it’s not something from the PSTN.

My theory is that the very sensitive speakerphone microphones in those models are picking up small noises, and then picking up their own playback of the noise, which leads to the feedback sound. It repeats, which is why it sounds like an echo.

I think turning rxgain/txgain down may make a difference, but I haven’t tried it yet. Has anyone else experienced something similar?

Justin Sherrill – American Rock Salt P: 585-991-6825 F: 585-991-6925 C: 585-298-6826

One thought on - Audio Feedback – Where To Troubleshoot?

  • Justin Sherrill wrote:

    That’s very appropriate for the season. I just hope they’re not Todash Chimes. ; )

    Your theory sounds correct to me. You’ve described acoustic echo and that is the most prevalent type for internal VoIP calls.

    I believe rxgain and txgain only apply to DAHDI channels. The first thing I would try is reducing the speakerphone volume settings on the Polycom IP550s.


    Matthew Roth InterMedia Marketing Solutions Software Engineer and Systems Developer