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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, sound travels at about 1125 feet per second (343 m/s) in air at 68°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 light appears instant here on Earth.
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—and it stays constant. It does not change—it is governed entirely by 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 adds up to over a quarter of a second.
Latency is where all of this starts to matter in a practical sense.
Digital audio, especially high-resolution 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. Today, from the moment a sound is made to when it’s heard, it usually passes through at least one digital audio device. And digital audio is, basically, data.
This is where the complexity begins. 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. Additional time is required to process digital audio, buffer it, and transmit it across a system. 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. In some cases, latency is so minimal it is imperceptible. In others, it becomes noticeable enough to affect clarity and listener experience.
Latency becomes most important in 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. With ListenWIFI, venues can stream audio over their existing WiFi network directly to their guests’ smart devices or dedicated ListenWIFI receivers. As a Listen solution, it delivers 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.
And we’ve recently introduced another digital-based assistive listening solution. Auri™, powered by Listen Technologies and Ampetronic, is the first installed ALS utilizing Auracast™ broadcast audio technology. So what is the actual latency? Let’s go to the Auri™ spec sheet:
31ms. That’s almost nothing-er.
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.
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We would love to answer your questions, provide you with a detailed quote, or send you more information.
