Mysterious Volume decrease from an old PBX caller.

[Noel Evolution]

Here is the scenario:

Client creates a conference call (webmeeting)

Their partner dials into the DID
They can enter no problem but their volume is 5 times lower than everyone else.

I got in touch with the client partner and called them from my 3CX system and could hear them well enough. I call them from my personal cell phone and they are perfect. (Here is when it gets goofy) He calls my cell phone and it is even better! He calls my 3CX extension and BLAM I cannot hear him we at all! Perfectly clear but 5 times more quiet just like the conference call.

I tried switching around the codec order to every combination and it does not change. When he calls either 3CX system, he cannot be heard at a normal level.

Ideas?

 

[leejor]

What type of device is the "partner" using to place the call. That I'm not clear on. What is the common denominator having the issue? The "partner", or a destination?

 

[Noel Evolution]

The partner is using a hardline corporate phone. (He called from several desks to get the same result)

 

[leejor]

Are the "corporate phones" 3CX extensions, or on a different PBX?

If the calls originate from another PBX, and you are unable to replicate the issue from other originating locations, then the common denominator would be something associated with, perhaps a "bad" trunk issue?
Could they be using analogue trunks (PSTN lines)? They may be "landing" on one with low level, every few calls.

 

[Noel Evolution]

sorry, I thought I was being specific when I said a hardline corporate phone. Yes, very old analog system. Every call from any extension is super quiet when they call us.

Thank you in advance

 

[leejor]

Then I would first suspect it is either a setting in their PBX (padding?), or a trunk issue. Many older PBXs used a pool of phone lines reserved for outgoing calls, or, in some cases lines shared with incoming, pre-PRI. If that is the case, then there could be an issue with a linecard, or setting,on one, or more of the lines at, or to, the CO switch. They may also be far enough from a CO to have loop-extenders on their lines, which can cause all sorts of issues if not set-up correctly. There could be an incorrect Pad level set in the CO switch against their trunk group. I've seen that happen. Even an additional 3db of padding, can make a noticeable difference to some destinations. There are many possibilities that can cause low levels. It sounds (no pun intend), as if they should have their support people/ PSTN provider, run level tests on all of their trunks.

3CX cannot compensate for audio issues originating at the callers equipment

 

[JohnS_3CX]

It's fairly simple at this stage, you just need to run a capture and hear the audio in Wireshark, coming in from your provider.

If you receive low audio volume packets, you don't need to even bother troubleshooting your end.

The provider may have *some* insight, namely checking their own end to discover that the inbound caller is also sending them low volume audio.

At that point, the matter lies on the person calling you. Not you or the provider.

 

[Noel Evolution]

It is just curious why the volume would be different when we call them. They are at a normal level.

When they call my cell phone, they are at a normal level.

When they call our reseller 3CX setup, they are super quiet. When they call the new 3CX instance that we just sold them it is super quiet.

What is it about 3CX that is incompatible with their system calling in?

 

[JohnS_3CX]

Obviously the route followed when they call your mobile is necessarily going to be different before it reaches your device so you get different results. This is probably where the answer lies, or a good starting point at least. Do your own test and if low volume is confirmed in your capture (RTP leg from provider to PBX) inform them accordingly and use the capture as evidence.

I suspect when they call you, the route followed via the providers and any transcoding taking place on their end, somehow affects the volume. That's why I mentioned the provider may have some insight by checking their own end to discover if the inbound caller is also sending them low volume audio, before they pass it on to you.

 

[Noel Evolution]

I don't have access to the partner company. They dial in to weekly conference calls that our client holds. This is going to be a deal breaker if they believe 3CX is not universally compatible. This person comes in loud and clear with their existing analog PBX

 

[leejor]

I would suggest that they speak with their provider, to arrange a trace of the low level calls. The call may pass through several providers, and a trace would have to be co-ordinated. The same trunk groups may not be used when calling your mobile, or calling back to them, explaining the difference in level.

 

[Noel Evolution]

Thank you for all of your help. I will pass the information along and hope that the pluses of 3CX outweigh the analog issue. Stay safe, everyone.

 

[leejor]

Providers typically add padding to trunks based on their destination. Generally, the farther the distance, the more padding, to accommodate echo suppressors. So inter city, normally 0 db, within a country, normally 3db, and internationality normally 6db. These are not hard and fast rules however, so there are discrepancies. When a new trunk group is established, padding levels are specified based on where the trunks go. If the padding is incorrect, or calls to "other" unintended destinations, are later routed over that trunk group, audio issues can happen. Calls do not always take the most direct route, and may pass though multiple providers, each can have an affect on the call quality.

 

[Noel Evolution]

This is a call from Alabama to Florida. FYI

 

[JohnS_3CX]

Thank you for all of your help. I will pass the information along and hope that the pluses of 3CX outweigh the analog issue. Stay safe, everyone.

That would not even be a point of contention if you just run a capture and collect evidence. It should put the customer's mind at rest.You don't even have to weigh the analog issue against the 3CX system in this case, avoiding a useless argument altogether.

Consider registering a DID from the trunk directly on a deskphone or generic softclient and have the other party call in. My expectation is that you will have low volume even when you've bypassed the PBX entirely.

 

[Noel Evolution]

the volume issue only happens when calling a 3cx system. I had them call other systems we have set up in the past. FYI They don't want for us to investigate further as it is an inconvenience to have them help troubleshoot with us.

Thank, regardless