Call quality suddenly became a big deal last week when many reviewers panned it. I finally activated the Evo 3D today and could test this. This is a subjective commentary, but I have a really good ear, and among friends, I'm the go-to guy for anything sound- and music- related, though I don't consider myself an audiophile (that's another story). Got a chance to have a 15-minute phone convo with a neighbor (a stereoscopy enthusiast, actually) and talked to him about the phone. I was prepared to have a very poor experience given all the negative reviews. But it did not turn out that way. I heard very very little background hiss. Higher frequencies were a little muted (some people call this 'muddy' sounding), but not so much that you couldn't distinguish an 'F' from an 'S.' That puts it on par with landline quality. Actually, hiss has nothing to do with call quality in the digital era. Here's a little background and explanation: Hiss was intentionally added to land lines back in the day to let people know a line was established. The dead silence made people think they were disconnected. In the digital era, noise reduction filters often removed all hiss, making silent parts of the call truly silent. Many mobile phone and VOIP carriers added 'comfort noise' to re-solve the old problem. Have you ever pulled your phone from your ear and look at it to see if it's still connected? If so, your carrier probably doesn't use comfort noise. But if the carrier of the person on the other side does use comfort noise, you'll be able to hear it. Hiss in the audio world is the same as static on a TV. It's white noise, and only in an analog transmission do you have various degrees of static/hiss. With digital transmissions, either the signal is strong enough to interpret, or it isn't. 1 or 0. Nothing like 0.28. Therefore, when someone gripes about hiss, they are likely griping about comfort noise, which is intentional, or the person on the other line is in a noisy environment. This point is often brought up when discussing HDMI cable quality. If a cheapo $1 Monoprice HDMI cable is working, you're getting the best picture possible. There's no in between. One scenario I left out was a defective speaker. Yes, that can cause hiss, since the speaker is an analog device, but it's very easy to test if the hiss resides in the speaker. Expect the hiss to always be there for every single call. If not, it's likely not the speaker. I actually use my phone as a phone, and my day job requires me to be on a call at least an hour a day, and I call people around the country and sometimes to India and China, so I am very familiar with what the Evo 4G was capable of in terms of call quality. Therefore I could usually identify which side the problem was on (signal cutting out, dropped calls, etc). Rarely was it the Evo 4G. And actually, the worst performing phones were the iPhones, which is very popular in upper management apparently. They get dropped like flies anyway... Evo 4G call quality sounds the same regardless if the bars (stock Sense) show 1-bar or 6-bars. Where it starts to fail is when the indicator shows 0-bars, and even then, it may not drop the call. Based on my signal strength testing in this thread, the Evo 3D bars correlate to the Evo 4G bars exactly. I watched the signal strength fluctuate, and both phones went from 3-bars to 4 at the same threshold. I also witnessed this consistency going from 4- to 5-bars. So I'm going to assume HTC didn't change how they represented signal strength in their bar indicators. Today, during my phone call, I had 2-bars, and the call sounded clear. I would feel confident saying that you should still have good quality at 1-bar, just like the Evo 4G did. If you have a stable 2-bars or higher, and your call quality is bad, I would point the finger at the phone on the other end. A good idea is to call someone on a landline, where you know their call quality will be constant, at least on any of the major US TelCos. So that's what I did for my next test. With a stable 2-bar signal strength on my Evo 3D, I called a landline (parents' house). No one was home, but I got the answering machine, and I know the sound quality of that answering machine well, having heard it for at least a decade. Evo 3D sounds just fine at 2-bars. In summary: call quality, is it awesome? No... but I'm not expecting studio-recording fidelity on a phone. So, for what it is, it's very good. It captures the upper frequencies enough to distinguish all the consonant sounds, and it holds a signal consistently (no large fluctuations in signal strength or bars indicator). At 2-bars, calls sound just as good as the full 6-bars. Hiss during my test calls were negligible, and as I explained above, hiss is not a relevant indicator of call quality in digital transmissions. Again, this was my subjective opinion, qualified by my understanding of sound, basic DSP, and the industry's use of 'comfort noise' to generate hiss. Comments and/or criticisms are welcome, as always. UPDATE (June 26, 2011): I found a way to test call quality on both Evo 4G and #vo 3D despite the 4G now being deactivated. Dial *2 and listen to Sprint's IVR. I did the following tests: 1) E4G + Airave 2) E3D + Airave 3) E4G - Airave 4) E3D - Airave With the airave, both E4G and E3D performed very well. Very little hiss and very clear consonants. I observed 4- to 5-bars. Without the airave, I got 0- to 1-bars, but the audio never cut out. I noticed some volume fluctuations, but still good for both phones. Now here's where things got interesting... I decided to output the call audio through the headphone jack to my sound card and record it with Audacity. And I found that while the E4G recording sounded pretty much the same as the earpiece, the E3D sounded HORRENDOUS. Very loud hiss and very muffled voice. Consonants were very muddy. It was night and day. I repeated the E3D calls a few times just to rule out a fluke connection. It was always bad. That would certainly explain some of the bad reviews. If they made their determination solely through an audio-out through the headset to speakers, that would explain the discrepancy. So it proves that call quality through the headphone jack is pretty bad. But call quality through the earpiece speaker and the back speaker sound just fine. I've attached the recordings from trials 3 & 4 (no Airave; 0- to 1-bars) for your listening pleasure. Again, this test seemed to indicate a problem with E3D's call quality through headphone jack only. And I haven't tested BT quality in my car yet.