Physics.

Quote:

The velocity of sound increases slightly with higher temperatures. For example, at an elevation of 0 feet above sea level, at a temperature of 50 degrees (Fahrenheit), sound will travel 110.7 feet in 100 milliseconds (ms).

At 90 degrees F, it will travel 115.14 feet in the same 100 ms. This will force the wavefront angle of sound from loudspeakers to track slightly downward, bending toward the cold air layer.


Now let's round things off in order to make it easy to investigate the situation.

Let's work with an easy, centralized figure of sound traveling at about 100 Feet in 100 milliSeconds. Good "rule of thumb" for fast calcs in the head on this subject, BTW.

At 2.5mS actual audio latency, the "delay" involved would be the equivalent of playing live with others who were -- 2.5 Feet away from you.

A 25mS latency would then be the equivalent of playing along with someone who was 25 feet away from you.

Also, the reported mS Latency figure in the computer can vary as much as 100% - simply because some softwares report a "one way" figure as to latency in mS, others report a "round trip" figure, or the amount of time it takes for the signal to go into the computer, get processed, and come back out at an audio output for monitoring purposes. Still, when the latency is below around the 25mS mark, not very many can really notice the difference when faced with a true double blindfold test on the subject. To date this engineer has found not one musician who could pass that test, regardless of musical prowess or what they THOUGHT they could detect.

Bottom line, a true 2.5mS, or even 6mS audio latency is indeed not detectable by human beings when the subject is sound waves.

http://www.prosoundweb.com/article/print/whats_the_delay_the_effects_of_weather_conditions_on_sound

Today's modern sound reinforcement engineers can work wonders using software-defined time alignment, based on the same physics.

The most recent outdoor Country Music Festival event, the sound engineering actually made history with such a purpose-designed and tuned system. Zero Latency anywhere in the live venue, onstage or anywhere in the audience.

Unbelievable large venue live sound situation. Curt Jenkins led the sound engineering. Wow.

Listen to it, that is Live realtime audio feed, man.

The performers enjoyed near-studio audio intimacy at the same time. Multiple acts, rapid-fire, too.

The audience is able to SING ALONG, in a large stadium venue, in realtime with the band when they are called upon to do so. (!)




How it was done:

http://www.prosoundweb.com/article/cma_music_festival_rocks_music_city_with_l-acoustics_k1/

Today, we KNOW what the true parameters of human perception of audio latency is, the modern sound engineer must also tune the system for the realtime Barometric Air Pressure and Ambient Temperature - and they can, and they do.

This ain't Woodstock with the Altec Lansing power amps that used tail light bulbs as emitter resistor "compression". Not hardly.


--Mac

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