So perhaps this can feed into the rating system, total latency < 50mS is an A, < 150mS is a B, 600mS is a C or something like that.

Simon

On Thu, 25 Feb 2021, Simon Barber wrote:

The ITU say voice should be <150mS, however in the real world people are 

a lot more tolerant. A GSM -> GSM phone call is ~350mS, and very few 

people complain about that. That said the quality of the conversation is 

affected, and staying under 150mS is better for a fast free flowing 

conversation. Most people won't have a problem at 600mS and will have a 

problem at 1000mS. That is for a 2 party voice call. A large group 

presentation over video can tolerate more, but may have issues with 

talking over when switching from presenter to questioner for example.

I worked at a phone company 10+ years ago. We had some equipment that 

internally was ATM based and each "hop" added 7ms. This in combination 

with IP based telephony at the end points that added 40ms one-way per 

end-point (PDV buffer) caused people to complain when RTT started creeping 

up to 300-400ms. This was for PSTN calls.

Yes, people might have more tolerance with mobile phone calls because they 

have lower expectations when out and about, but my experience is that 

people will definitely notice 300-400ms RTT but they might not get upset 

enough to open a support ticket until 600ms or more.

-- 

Mikael Abrahamsson    email: swmike@swm.pp.se