Sticklers will no doubt object to my claim that AM radio is 5 KHz. In the US, the RF channel width is 10 KHz, however AM radio in the AM broadcast band uses double sideband. That makes audio quality limited to 5 KHz in theory, and often no better than 3.6 or so KHz in practical receivers.
Also, during the day, it's possible for AM radio stations to expand their channel width. But in practice that buys you very little. Most AM receivers aren't set up to use the wider band. And at dusk, all of that goes out the window anyway.
As one who finds all voice telephony quality to be pathetic, whether land line or cellular, analog or digital, I'm also interested in seeing drastic improvements. I can only imagine how much more useful teleconferncing would be, if we weren't tied to traditional telephony standards.
From the days of analog telephones, the voice bandwidth was limited to a 4 KHz channel, so that means a practical passband of about 3.3 or perhaps 3.5 KHz. As bad as most AM radio in practice, although worse than AM radio in principle (where channel width is 5 KHz in the US).
That's why voice telephony sounds like the other guy is covering his mouth all the time.
When digital telephony came to be, that 4 KHz channel width was deemed good enough, and the standard 8 KHz sampling rate used in digital telephoney made darned sure that we wouldn't get anything better.
HD voice doubles that passband to 7 KHz. That should improve matters a lot. Although Skype, unhampered by any of this, can sound even much better than HD voice (assuming a decent broadband connection and that both sides have the latest codec).
LTE has been predicated on the promise of high-speed mobile broadband access, but subscribers will still expect to make voice calls on their devices, so audio quality needs to be assured. The success of services like HD voice and voice over LTE (VoLTE) depend on device and network performance, and audio quality performance testing is a critical component of LTE testing.
I am wondering about the differences in voice quality between voice over LTE and voice over 3G. Can anyone give us any pointers? And what about HD voice? How is that different from other voice?
NASA's Orion Flight Software Production Systems Manager Darrel G. Raines joins Planet Analog Editor Steve Taranovich and Embedded.com Editor Max Maxfield to talk about embedded flight software used in Orion Spacecraft, part of NASA's Mars mission. Live radio show and live chat. Get your questions ready.
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