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Wednesday, April 3, 2013

Get Ready For Wide-Band Phone Audio

HD Voice image from Bobby Owsinski's Big Picture blog
From almost its beginning, the telephone has suffered from a bandwidth that has been restricted to around 300Hz to 3.4kHz. Some of the band limiting was due to the limited range of the transducers used, but also by intention as well. By limiting the bandwidth to only those frequencies that humans hear well, transmission was more efficient, which was extremely important in the early days of electronics where small tube repeater amplifiers where necessary all along the telephone line for it to work.

Through the years phone audio gradually became a little cleaner, mostly thanks to the digital encoding techniques introduced, but the bandwidth basically remained the same. Of course, you could always order a high-bandwidth ISDN line to do some serious recording via the phone, but this was somewhat expensive and a little tricky to set up (at least when the technology was first introduced). To give you an example, this used to be done with the Capitol Records Studios all the time so people could take advantage of their wonderful reverb chambers without actually mixing in their studios.

That said, the limited phone bandwidth is all about to change as AT&T begins to roll out its HD Voice feature later in the year as part of its 4G LTE network. The company will double the sample rate to around 16k and be able to deliver a much improved 80Hz to nearly 8kHz bandwidth as a result.

This isn't exactly the first time something like this has been done before, as many European carriers have had HD Voice equivalent for years, as does many VOIP networks and online carriers like Skype. That said, US cell phone service pales in comparison to the rest of the world, so we'll gladly take any little improvement whenever we can get it.

For all you geeks, AT&T plans to use the AMR-WB codec, which stands for Adaptive Multi-Rate WideBand in the new system.

One bummer is that you have to be talking to someone on a network that supports HD Voice for you to hear it, but you probably figured that out already.


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