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Comment by Aloha | Hacker News Reader

A cell phone tbh, is about the same latency as a landline in most end to end call circumstances. Latency only really is noticeable when better than 600ms. (And only a real problem over 1000)

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Do you have a citation for that? I've heard 200ms as the key threshold and the ITU uses 100ms for their default delay sensitivity class[1]. One key concept is that this isn't fixed but situational: if you're watching a TV show, the threshold is higher than if you're trying to react to something which is higher than simply noticing a delay and speech is more forgiving than, say, music hitting a precise tempo (I believe musicians have been tested as noticing delays down into the 10-20ms range).

One other big factor is consistency: if the variability is due to compressor overhead which is constant, the effect will be noticeable but less distracting than if it's varying due to something like wireless conditions.

1. https://www.itu.int/rec/T-REC-G.107-201506-I/en

I know that if the delay is constant, a good musician can compensate for it. I think it's a lot easier to hear that two things don't happen at exactly the same time than it is to tell whether two things happen 200ms or 300ms apart.

Musicians have that internal metronome to compare things with.

I disagree with these numbers, in general. Though of course "noticeable" is subjective and varies by use case as well as by person.

For many people, end-to-end audio latency in a 1:1 conversation becomes noticeable/annoying at 200ms. And in a multi-participant conversation, talking over each other becomes noticeably more common even at 100ms compared to 50ms.

IIRC the Bell standard points out no more than 50ms.

I think latency is noticeable at even lower values. As a basic example, try to sing a song with someone over a voice call. Consider using Airpods or similar bluetooth headphones to make it more apparent.

Imagine trying to have a face-to-face conversation with 600ms of latency...

Do you have a source for that? Gaming latency is noticeable in the ~100ms range, and humans are highly sensitive to small adjustments in speech.

I would've thought it would be closer to the 200ms range, but I don't have any data to support that.

There is a huge quantity of research opposing your statements. The ITU considers 300ms round-trip latency to be catastrophic.

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