Distorted VOIP phone audio difficulty

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For years I have used Plantronics Supra binaural headsets along with the matching Plantronics headset amplifier/interface M10 or MX10. ( I am not at that location now.) I have the requirement that my phone audio be crystal clear at all times. I have never had any problem with clarity until yesterday. I never had considered VOIP because my internet speed was not ideal. Several months ago I got fiber and my up and down speed is 1 GIG with pings at 2ms. With this super speed I thought that VOIP would be an acceptable choice since it would save me more than 50% of my phone bill. Now that it is installed I am told that my transmitted voice is somewhat distorted and there is some sort of slight crackling in the background. I cannot live with this problem. I spoke to level one of tech support last night and he confirmed that I was indeed distorted. I have another line that utilizes the MagicJack. I phoned the tech on that line and the distortion was still present. I also switched from my headset and amp combo to a regular phone on the business phone system (Avaya Partner) and the distortion is still there. Level two is supposed to get back to me today and begin troubleshooting the problem. I was just wondering if any Expert has encountered this difficulty before? With such incredibly high isp speed the is the last thing that I had expected. If an Expert has any ideas please let me know.  

Configuration wise: On the isp's router there are two phone jacks. I go from jack One directly to the KSU of my Avaya phone system. The magicjack goes to the phone system the same way. I must leave for a few hours but when I return I will hook a scope up to my transmitted and received audio and compare transmitted to received information with a dual trace scope to see if that tells me anything. Ideas?? Things to try??
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nociSoftware Engineer
Distinguished Expert 2018

Commented:
Speed is one thing, the right codec is another, and QoS support in a router another again.
If you have heavy other traffic running on the line (say a download that goes > 500Mbps.).., then VOIP may  have interference from that.
A router that cannot cope with the speeds can be an issue.  Some Codecs have better properties then others.

You may need to reserve some bandwidth in a router (f.e. upload may NEVER use >90% of bandwidth) and as you can only control sending of data traffic going out on the internal port of the route should likewise be limited.

Routers with Too much buffer space may be worse than ones with smaller buffers (aka "Buffer Bloat")
The local net including the router (also the ISP) should conform to QoS settings. (Where VOIP traffic should be slightly prioritized).
Top Expert 2016

Commented:
the magicjack should plug into one of the LAN ports on the isp's router not the phone jack that is for a regular POTS phone
Need -a- ClueRESEARCHER

Author

Commented:
Noci.. THANK YOU! I was speaking to a level 2 tech when I read him your response. He identified with each of your points. The distortion was not evident today for some odd reason. I do have two other related questions for you or any other expert.

1. Is there a published SPECIFICATION that lists a minimum frequency response and noise level for VOIP? I have nothing concrete to compare my setup to in order to evaluate if my service is what it should be.  I would just guess that it might be something like 100 to 7,000 Hz +- 3dB. ONLY an off the cuff guess. Does such a spec exist?
2. Is there a software application that I can run on my computer and also on  the isp's computer that tests for compliance? Or, since I have the isp phone VOIP and a Smartjack VOIP I could run a loop test between the two lines. I could devise my own test using any of many tone generators available, but there is probably a dedicated go/nogo or loopback test that would make this easier. In other words, I want to make sure I am getting what I am paying for. My ISP is very open to cooperate with me in doing such a test. Ideas?
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Software Engineer
Distinguished Expert 2018
Commented:
1) Not that i know of...  the minimal support should be for aLaw or uLaw ( EU or US standard for voice communication, both sample 8Khz - 16bit LMP companded down to logarithmic, 8 bit samples. )  Which is equivalent to ISDN quality. this is also known as G.711 format.   other formats with other characteristics do exist, mostly better compressing so less bandwidth is needed.

2) Hard to do. All data compressing is done to have best throughput of VOICE data by compressing according to voice models. That is why FAX'es need to be handled differently.  FAX accros aLAW/uLAW is doable, with other compressions it will just fail.
Using tone generators might not give a uniform response on the complete spectrum.  (You can test of course)

For FAX there is also T.38 where IF 2 fax machines supporting it are talking and see they have a digital connection then the data will not be sent as audio but rather as a digital stream. (Although the connections starts as audio for compatibility).

The original telephone systems must be at least reached.   Also keep in mind that telephone systems may transcode from one format to another if there is no common support for formats
(f.e. a EU set using aLAW talking to a US set using uLaw, it is up to the PBX to set this up). Or You talk using a VOIP set to someone on a GSM network using GSM compression method.
GSM != uLaw/aLaw
You may be able to add distortion by also starting massive data transfers while talking. f.e using iperf, netio or many file transfers. Try to saturate the line. iperf & netio attempt to measure bandwidth capacity so they be the simplest way to saturate a connection.
Need -a- ClueRESEARCHER

Author

Commented:
noci - Let me tell you that I REALLY appreciate your obvious in depth response. However, your level of competence and my lack of knowledge about VOIP make it near impossible for me to grasp. In other words, I don't understand all you are trying to teach me. However, I am positive that your answer will help because I will show it to the Level Two technician that is helping me out on this situation. For the time being I will consider this my answer and again I thank you. Cameron
Need -a- ClueRESEARCHER

Author

Commented:
Oh David, I just noticed your response when I refreshed. My Magicjack is plugged into MY router and the output then into the Avaya business phone system as one of the CO lines. It has worked fine for over a year. However the technician did say that the distortion ( which is not horrible ) was also heard on the Magicjack line. I am sure that it will get sorted out in a few days since this is a most unusual situation I am told.

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