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Ask the Expert: Voice Quality Issues You Might be Facing

Lisa Latour
Frequent Contributor
Frequent Contributor

This is an opportunity to learn and ask questions about voice quality issues that you might be facing your environment and troubleshooting with the tools and techniques available within the platform with Cisco expert Malick Irfan Alvi.

Ask questions from Monday, May 25th, 2015 to Friday, June 05, 2015

Poor audio/video quality is a very common problem seen with PSTN calls as well as IP phone to IP phone. Poor audio quality causes a huge impact to the user/customer experience. Poor audio quality can be classified in primarily in two categories – 1) Over the TDM PSTN  2) Over the IP. In this session, we will look into how to effectively troubleshoot both using built-in tools and 3rd party tool available.

Cisco expert Malick Irfan Alvi will cover and answer all of your questions about troubleshooting voice quality issues.

Malick Irfan Alvi, CCIE Collaboration #45777 is a Customer Support Engineer for the MultiService team in Richardson TX. Malick has over 12 years of technology and service industry's experience with MS in Electrical Engineering from Wichita State University, Kansas. He also holds bachelor of engineering degree in Computer & Information Systems from NED University of Engineering & Technology Karachi, Pakistan along with other Associate and Network Level Certifications. He has in-depth knowledge and understanding of IP networks, “traditional” voice & IP voice communications systems applications and protocols. 

Malick specializes in Unified Communication Technologies including Cisco Unified Border Element (CUBE) & Session Border Controller (SBC), Cisco Unified Communications Manager (CUCM), Cisco Unified Communications Manager Express (CUCME), Cisco Unified SIP proxy (CUSP), Voice Gateways, Faxing over IP, VXML Gateways and Media Quality Issues.

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8 Replies 8

Gerardo Urrusti

I have CME upgraded to a new version 10.5 with 7965 and 7962 phones updated to the latest software which comes with CME load. When dialing outside calls the voice quality on the 7962 and 7965 phones is very bad. We are using 8 FXO lines for PSTN. We have like a Echo and delay in the conversation some words are not heard properly and it is only happening on PSTN calls, if we calls between Phones the voice quality becomes much better. Mostly voice quality issue on the external calls happening in the start of the call.

Can you please help.

Hi Gerardo Urrusti,

Echo and first few words clipping is very common problem on FXO line. The reason is that, every FXO line needs different gains and attenuation setting  as well as Echo cancellers setting. The echo heard by the IP phones is most likely being caused by the hybrids on the PSTN.

Please look at this link.

Further more, you can try THL Tone Sweep Method to find the right settings.

Please look at following link.


I have CUCM 10.5 with Cisco 7821 and 7945 endpoints. Internal calls are fine. However, I get voice quality issue with outbound calls from Cisco 7821 endpoint. The lost packet rate is always about 2 % with just Cisco 7821 series. Meanwhile, I don't get any lost packets with Cisco 7945 endpoints in same outbound calls. My attached files are call statistics of them.

I also try to test by moving the Cisco 7821 the  closest with the voice gateway ( same switch). But, there is still lost packets.

Any ideas for me?

Hi Fernando Mondragon,

Looks like you are having issues on your 7945 phone negotiating g722u inplace of G711u. If you notice on sender codec in 7821, you will see that its doing G711. Where as on 7945 phone it is saying codec received as G722. 

This will cause voice quality issue if G722 is negotiated in place of G711. I have seen that G722 can be negotiated in place of G711u since model  phone such as Cisco 7942/62 and 7965/45 phone can do both G722/G711 codec. G722 is preferred codec for 7945 phone. The 78XX phone prefer G711. This will cause wrong codec to negotiate causing voice quality issue.

Please try disabling this under the device page on 7945 phone; 

"Advertise G.722 Codec"

Once we made sure that its successful, we will disable it  in Enterprise Parameters for all phone. 


Mariana Llamas

Hi Malick! - Thanks for posting this discussion. We upgraded from CME to full blow CUCM 9.1 deployment as our office has grown. We used the 3825 router running as CME to act as a CUBE. We are running 8951's, 9951/9971's, 7965's, 7942's, 7962's and 7937's. And some older 7940's. Call quality on the 7940's are great while the 7965 and newer model phone are bad. There is a tunnel sound with a clicking sound going on. We've updated the firmware and then downgraded trying to get through this on all phones.


If we put a 7940 in its place, the call quality issues goes away. Also when we change the codec between the phone to G729 there is no issue with Voice Quality. Any ideas?

Hello Mariana Llamas,

Since you upgraded from CME to CUCM, I believe that issue started after the upgrade. As you mention that issue is only with 7965 and other newer model of the phones, and, older 7940 phones are working fine. Furthermore, changing the codec from G711u on the phone to G729r also fix the issue. The issue seems to be G722 Codec problem with G711ulaw. 

If you make a call on 7945 or newer model of the phone and check the statistics (Tap "?" two times) you will notice that G722 codec will be showing up as Receiver codec. On 7940 phone you will see that codec is G711ulaw.

Please try disabling this under the device page on 7945 or newer phone; 

"Advertise G.722 Codec"

Once we made sure that its call quality is good after the change, we will disable it  in Enterprise Parameters as well as System Parameters for all phone. 

Login to CUCM >> Browse to System >> Enterprise Parameters >> Search for Advertise G.722 Codec >> disable it

Login to CUCM >>> Browse to System >> Service Parameters >>Select the CUCM server and the CallManager Service >> Select_cm_service >> Search for G722 Codec >>> disable it


Dani Ma

I am having intermittent issues with call quality. I would like to see if there are any debugs or traces on CUCM or on PRI gateway I can enable to troubleshoot the issue. I have checked cdr record and it shows no jitter. I have checked the stream1 on the phone and max jitter is between 20 and 18 most of the time. Do you think if issue is with firmware related. Can you please suggest me what else I should be looking or enabling to see where the issue lies traces, show commands, debugs etc??

Hi Daniel,

Voice Quality issue needs to be troubleshoot real time since issue is happening to RTP (Real time protocol). There are not much debugs or traces which will be helpful. Best troubleshooting would be to take packet captures such as Wireshark, PCM capture and so on..

Please see following link which will be helpful in your case 
Since you are using PRI gateway and getting intermittent issues with call quality, I would ask you to configure Trigger PCM capture. The best would be to open TAC case since PCM files needs to be decode which can only be done by TAC. You can collect PCM your self to speed up the process. The above link talks about the steps to collect PCM. 

Also following is a good link to take PCM capture 

Please let me know if you still have any questions.


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