Sound quality

Hi all, We are having some issues with our sound quality recently. When you make or receive the call the sound becomes “metallic” for few seconds then it gets back to normal for a minute or two and back to the “metallic” again for some reason. As far as I’m aware we’ve not been making any changes to the set up for some time it just started to happen for no reason about two weeks ago.

Thanks in advance

Need more info,

Codec, version,gateway,etc

Codecs - ulaw,gsm,alaw
Gateway is online and working.

As far as I know, and I’ve suffered, robotic/metallic voice could be a symptom on not having enough bandwith for the call.

Just giving an idea to verify, I’m not even close to be a FreePBX nor Asterisk expert, but it could help.

Who/What is your gateway.
What is your internet connection?

You would have to say more about how you installed FreePBX/asterisk and on what hardware, what you describe could be any number of things from an overloaded cpu, an overloaded network, or perchance your choice of virtualization if appropriate.

Right, the Gateway is Gradwell, internet connection is ok… see screenshot

with regards how it’s installed, well it wasn’t me who installed it, it was previous IT guy in my company, for some reason we’ve got Elastix and FreePBX installed, or FreePBX installed on Elastix. The CPU is not overloaded. Hardware is HP Proliant DL360G7 with VMware installed on it. There’s no unusual higher traffic on the local network as we only got few ppl working in the office. Basically nothing has changed between the time when it all worked fine and the time when we started to have the problems.

Thanks in advance for all your help

Screen from VMware

Possible areas of trouble:

  1. A problem with FreePBX itself. IMO unlikely, given that you didn’t change anything.
  2. Another virtual server on the Proliant is consuming resources such that Asterisk can’t get what it needs.
  3. A problem with your Internet connection.
  4. A problem at Gradwell.
  5. Unexpected or unwanted traffic saturating your Internet connection.
  6. Heavy LAN traffic saturating a switch or router.

The Visualware test by itself means nothing, because the data reception phase (while the green progress bar is advancing) takes only about 15 seconds, and most of your 15-second intervals are unimpaired. However, if while the bar was advancing, you were on a call having quality problems at the time, that would be strong evidence against (3) and (5).

Do you have quality issues on calls within the office? If so, that likely eliminates (3), (4) and (5).

If internal calls are good, but you have quality issues on calls from internal to external extensions (teleworkers or phones at a branch office), that would point to (3) or (5).

Do you have any trunks other than Gradwell? Do they also have the trouble?

You might try temporarily configuring a phone to access the Gradwell trunk directly. If they accept unregistered calls and you set the phone to not register, you should be able to make outgoing calls without interfering with the PBX. If they have the quality issue, you have practically eliminated (1) and (2).

Also, does the remote party also hear the metallic sound?

Personally I would try either real hardware or another hypervisor, KVM works well, VMWare , not so much.