Understanding Latency – What It Is and Why It Matters 

We get a lot of questions about latency.  Just one question really, but from lots of people, like, “What is it?”.   In the world of audio, the simple definition of latency is this: the time it takes for a signal to get from one point to another.  But let’s put it in context.

In acoustics, the speed of sound (in air) is 1125 feet per second (343 m/s) at 68 degrees (F) at sea level.  So, sound takes almost five seconds to travel 5280 feet (one mile).  Temperature, humidity, and altitude affect it slightly, but that number is the common baseline.   Light, on the other hand, is several orders of magnitude faster than sound — 186,000 miles per second (300,000,000 m/s), for those keeping score at home.   For practical purposes, we can say that, here on Earth, light is perceived instantly.  It’s that fast.  

We’ve all had the experience of seeing lightning and then hearing the thunder, later.  The same applies to hearing a jet in the sky and looking up to notice the plane is ahead of where you’re perceiving its sound.  Or being some distance from speakers at an outdoor venue and noticing a delay between what you see and when you hear it. 

In acoustics, that auditory delay is commonly referred to as, well, delay.  It is real, predictable, and measurable.  It is a constant.  It does not change.  It’s physics!  Delay time is typically measured in thousandths of a second – milliseconds (ms).   As a reference, it takes 267ms for sound to travel the length of a football field (300’/1125’).  That’s over a quarter of a second.

Latency… we’re getting there.

The advent of digital audio, especially high-resolution digital audio, brought many benefits – it is easily stored, offers endless processing and editing options, and can be copied without the loss of quality, just to name a few.  Digital is now the standard platform for virtually every audio application.  So, from the time a sound is made to the time it’s heard – if it goes through any sort of audio device — the odds are the sound has gone through at least one digital audio component.   And digital audio is, basically, data.  

And that’s the thing.  Turning analog audio into digital form, and vice versa, requires converters and it takes a tiny little bit of time for the converters to do their job.  That little bit of time is called latency.  It takes another tiny little bit of time to process digital audio, a bit more to buffer it, and more to transmit it.  All those are additive, so several elements of a digital audio signal path can, ultimately, impact, the time it takes for the signal to get from one point to another.  Though real and measurable, unlike the acoustic delay discussed above, digital latency is not a constant and the variables are many.  Latency can be so minimal that it has no noticeable effect – we call that low latency.  It can also be long enough that it is distracting, decreasing intelligibility — we call that a nightmare.  

Latency most comes into play with real-time audio applications.  Live public address, live music, live broadcast, live classroom, well, you get the picture.  In these examples, excessive latency would be detrimental to the listener.  It is critical that what we see and hear be in sync, especially when it comes to our world, our passion: assistive listening and language interpretation solutions. 

The good news is latency can be minimized.  Superior product design, conscientious engineering, top-quality components, and application of best practices can result in exceptional audio products with low latency and no noticeable delay.  That is why, at Listen Technologies, we talk about latency, publish latency specifications, and deliver products that offer industry-best low latency performance.

Take ListenWIFI for example… a venue can stream audio over their existing WiFi network directly to their guests’ smart devices or dedicated ListenWIFI receivers. 

Because it is Listen, you know it provides excellent audio quality and ease of use.  And now that you know about latency, you’ll find this ListenWIFI spec particularly meaningful:

That’s right, 40 to 60ms.  That’s almost nothing.

At Listen, it’s not just about audio, it’s about the entire experience.  If you’ve ever viewed the Our Story page on this website, you’ve seen this:

Listen Technologies enables venues to entertain, teach, and engage with the world and its limitless possibilities by delivering the right information at the right time and place… seamlessly.

The “at the right time” part… it’s real.  Just Listen.  

Written by Larry Lauzon