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Muffled sound

Discussion in '3CX Phone System - General' started by sohc, Feb 25, 2014.

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  1. sohc

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    After shifting from NEC to VOIP setup, some users said that the sound quality is a bit muffled.

    This is my current setup:

    3CX 16SC Pro
    2CPU - 8GB RAM - SSD drives - dedicated gigabit port (Hyper-V VM)
    Cisco 2960-S 48 port POE (Vlan 1 data and Vlan 100 voice)
    Yealink T46G handsets - G722 is the preferred codec
    Cyberoam50ing - Gateway with SHDSL and 2x ADSL backup. The 5MB SHDSL is dedicated to VOIP traffic with QoS for 3CX traffic.
    Engin Australia - SIP trunks provider

    What could be the cause of the problem? Is it 3CX, yealink or sip provider?

    Appreciate any response.
     
  2. lneblett

    lneblett Well-Known Member

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    This could be a tough one as it is rather subjective.

    What codec is in use between the phone system and the provider?
    Do the folks sense a difference in the call quality between extension to extension calls versus inside to outside or vice versa?

    The g722 codec is not typically used by most SIP trunking agents. Most will use the G711/u or a or the G729 codecs.

    If the calls going from extension to extension have the complaint, then I would tend to think it may just be the Yealink phones. This is not to say that the phones are defective by any means, but rather that they have a different frequency response or tend to highlight some aural frequencies over others that the NEC did not. You can always test using another brand of phone or even with an ATA and an analog phone. If you still have some of the NEC phones around, you might even take a handset and see about changing it out with the Yealink handset as a test or even using a headset. If it is the phone, then you have likely identified the issue, but the resolution may be more of an issue.


    If the issue is mostly involving external calls (calling in or calling out), then it could be your codec or the SIP provider. Maybe the provider is forcing a lower codec to preserve bandwidth or is having to transcode more than most. You will need to examine some calls and see what the codec is.
     
  3. sohc

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    Hi ineblett,

    Thank you for your response.

    I was able to solve the issue by changing the codec to PCMU and PCMA as the 1st and 2nd preferred codec. I didn't know that PCMU and PCMA are G711.

    I also changed the codec settings in the SIP provider.

    Cheers 8)
     
  4. sigma1

    sigma1 Active Member

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    If you are in the US, drop the PCMA aka g711a (Euro de facto standard). Thanks for sharing your experience, now I know of another phone, besides the Snom m9 that has a bad G722 HD audio...
     
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