It only takes a small amount of latency (5 ms or so) to noticeably impact performances by musicians. Latency is also an issue when you want to monitor a live signal along with other recorded audio, like in a DAW. It is not as big a deal with a playback only device.
rule of thumb is that sound travels roughly 1ft per ms, so 5ms is the same as standing 5 extra feet from the speaker. Most musicians don't have much trouble up to around 10-20ms.
Jitter is killer though - if the latency is randomly changing it's really annoying.
Is the speed of sound relevant in most recording scenarios? Assuming headphones and instrument/vocal mics that are within a few inches, then everything is traveling as electrical signals at the speed of light.
Or is this just meant as a visualization of latency in these scenarios versus what it would be like with musicians playing x ft apart from each other in a room?
I recently played on an electronic drum set and it was absolutely fine with headphones. But when we hooked it up to the speakers across the room there was a very noticable delay (~5ms as we calculated) when hitting the pads with the stick.
Since I only used acoustic drums until then I never gave much thought to the idea of having your drums sound delayed. It was quite eye opening.
It absolutely is. Many times when rigging halls for recording live events I've had to insert delay in to sub mixes to match latency to the back of the room. It's standard fair for a live audio tech (a thing I do on the side occasionally)
> Assuming headphones and instrument/vocal mics that are within a few inches
It is relevant, and monitoring via headphones or a floor speaker is a mitigation.
It's also a problem for large orchestras. If everyone else just plays along with what they hear from the people near them, the timing is going to be inconsistent across the orchestra pit even if you have some obvious audible reference like loud percussion. The mitigation is to orient yourself as much as possible around the visual cues from a conductor.
That's a good point, and I'd imagine instruments like a church organ would suffer from this too, though I know in that case there are a bunch of other sources of delay, like the time it takes for the pipes to fill with air.
The latter. The point being that they are trained, comfortable, and proficient in those scenarios and the same translates to a (consistent!) software delay of up to 10ms.
I think the loudspeaker part was a comparison to understand it a little bit better.
"If the system processing your signal introduces a 20ms delay, it would be the same as standing 20feet away the loudspeaker you're using as reference."
Interesting, I wouldn't have expected it to be that low, though in the aircraft space, control harmony can be disrupted with as little as 20ms of delay between control input and control surface movement[0].
Do you have any research you can suggest for that 5ms number?
It's not that low. Up to 40ms (roundtrip) isn't a problem for solo playing, in my experience. And it's also a matter of training. Church organists learn to play with much larger delays.
I can deal with 10ms roundtrip, but not much more.
One issue is when you get some acoustic sound too (open headphones, bone conductance, singing) and pretty much any delay in the headphone signal causes phase interference.
With a virtual instrument you would usually not face the full round trip latency, but rather control latency (MIDI?) and audio output latency (usually 50% of roundtrip). So in the VSTi case that might be closer to 25ms than 40ms in practice. Often the latency jitter is quite dreadful in this case as the control signal is not synchronous to audio.
