Noise On Phones While Speaking…

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Asterisk Users 7 Comments

I have a new install and the customer is complaining that they hear noise on all calls, no matter if it is internal or external, desk phones or softphones. The noise is only present when the user is speaking, not the remote side. The remote side does not hear the noise, only the local user.

We are using Asterisk .1.8.11-cert8 on a CentOS 6 machine with a Digium AEX800 card and DAHDI 2.6.1. I really do not know how this noise is generated. Where can I look? Why would a SIP to SIP call have this noise?

7 thoughts on - Noise On Phones While Speaking…

  • Check to see what random stuff they have on their desk.

    We’ve regularly seen things like mobile phones (or cellphones to those of you across the pond 🙂 ) causing interference with VoIP phones. We’ve also of late seen some (especially Iiyama) monitors doing likewise
    – I suspect they have a fairly noisy 240v-12v transformer inside.

    Kind regards,

    Chris

  • Carlos Chavez writes:

    If you record the call (with Monitor or Wirehark), does the noise show up on the recording?

    /Benny

  • Carlos,

    I think the noise you are hearing might echo cancelation that is broken or set incorrectly. Maybe the card and asterisk are both trying to echo cancel?

    Mark

  • The card itself does not have hardware echo cancellation so we use MG2. I am not fixated on the card because this should not affect a SIP
    to SIP internal call unless the card is really defective and provides bad timing to Asterisk.

  • Carlos,

    Echo might be a possible cause of the noise but it is strange you hear it also on internal calls since they have very low latency.

    Can you record a short sample with this noise or at least ask your customer to provide a more detailed description of the noise ?

  • What is your timing reference

    “module show like timing”

    where your timing counts > 0

    I had strange noises with dadhi 2.5 had to roll back to dahdi 2.4

    hth

    2012/11/17 Valer Nur

  • Carlos Chavez wrote:

    Actually when bridging channels Asterisk acts as either a low level packet router (“Packet2Packet” or “Local” bridge – RTP packet is read in, minimally modified, and immediately sent back out) or as a higher level media forwarder (RTP packet is read in, dissected some, stuffed into internal data structure, shipped off to other channel, RTP header added, packet sent – although monitoring/recording/transcoding is involved it’s in that list of operations too). Timing from an external source isn’t used. So really, I’m fairly certain it’s something to do with your phones. If you could post a short snippet of a phone calling another and the bridge that occurs I could be more certain.

    Cheers,