Bad call quality Xperia Z5 Vodafone Operator

[RobertoDS]

Good morning

I've an Xperia Z5 with latest fw 32.0.A.6.200 and with operator Vodafone

Sometimes happens that calling my girl, with an Xperia Z3 with Vodafone, the call stars with a stellar quality, very high and really clear, cristallin sound, but sometimes, after one or two minutes, call quality becomes muffled, just as it could be closed in medium or high frequences, and we-together don't move any other settings or aren't on the move !

That's happening is very sad, because situation becomes very bad and differences are rapidly noted because at the first seconds call quality was really good and becomes bad, and together are hearing the same thing ...

What shall we or I do ?

In Settings-Call, I've only EQ, on Normal (prefering to Luminous), but are anymore available other settings just as it was on Z3 ?

[Lord_viridis]

It's because you have lost HD calling whilst on the call.
It's common in areas where 3g is sporadic or low bandwidth and sometimes the phone will roll back to 2g as it is a stronger signal.
Unfortunately HD voice isn't supported on 2g so you will notice this decrease in quality quite suddenly when it happens.
For the record tho, every phone I've had since Z3 has done this (including Samsungs and a HTC) since the HD audio for calls was rolled out with both Vodafone and O2.

[RobertoDS]

Thx for the reply

However I'm connected, usually, to wify, and 4g/3g's not connected to, but I'm on 4g(prefered)/3g/2g auto !

It's denoted by me and my girl with Z3 (3g*2g because hasn't 4g) !

What could it be ?

[Lord_viridis]

Even if you are on wifi, the network being used is still either 3g or 2g, in idle it will seek out the strongest signal (in your case 3g as the call starts HD audio) but in call it will change to seeking out the most steady (2g almost everywhere in UK) and eventually will drop down to 2g and lose HD audio.
It takes one party to drop down to 2g to lose HD so the only way to keep it is to set network to 3g only (network dependant as I'm on o2 and that is one of the network options) if you have that option then it will keep HD audio only if both parties remain on 3g.

[RobertoDS]

I've

Only WCDMA
Only GSM
WCDMA (Prefered)/GSM
4G (Prefered)/WCDMA/GSM

I can't do better than this ...

I clearly put my choice on 4g prefered because I'm paying for 4g so it's useless to let stay out of games.

So what Can I do ?

[Lord_viridis]

Only wcdma is 3g only.
Try that.
Both of you, then call.

[RobertoDS]

I'm paying for 4g so I can't, obviously, put 3g only but then with 3g only I can't do HD Audio, that's available only in 4G

However when I'm in 4G, call goes directly to 3g, and once I close the call, phone goes to 4g

[Lord_viridis]

HD audio is 3g, 4g is used only for data on Vodafone

[Lord_viridis]

Apologies 4g is also used for volte on voda but that is not the same as the 3g HD audio in calls, same result, different tech.

[Lord_viridis]

However, you are not getting 4g calls (volte) as when you connect a call it drops to 3g instantly.
The only way you can get HD audio constantly in calls is by selecting "wcdma only" but yes, you lose 4g data which may not be beneficial.