Hey, are you there? Can you hear me now? Mobile data networks seem to improve by leaps and bounds every year, but cell phone voice quality seems to have stood still for decades. If you think your calls sound lousy, you're probably not wrong. The frustrating reason comes from our good old free market: Our mobile phone carriers just aren't talking to each other well.
The word "phone" has become pretty misleading when it applies to our little pocket computers. Sure, in 2016—the last year we could find data for—Americans made 2.751 trillion minutes (PDF) of wireless phone calls. But that pattern of calling has remained basically flat for a decade, while the use of data services on phones has been skyrocketing.
Add to that the fact that, a while ago, our carriers decided to use unlimited call-and-text packages as their base price, and make money from data packages, and you don't end up seeing a lot of marketing or excitement around voice quality.
But it turns out there's a big difference in voice quality between carriers, phones, and even calls on the same phone. And you don't have to settle for lousy call quality.
Check the Codec
This next bit is going to be an alphabet soup. High-quality voice calls need a good codec running over a good network. A codec is a method of encoding sound as digital data. MP3 is a codec, for instance.
The CDMA and GSM cell phone worlds developed different sets of codecs. GSM carriers, such as AT&T and T-Mobile, went with the AMR (adaptive multi-rate) family. CDMA carriers, such as Sprint and Verizon, initially chose EVRC (enhanced variable rate codec).
There are narrowband and wideband codecs. The wideband ones (often called HD Voice) sound better, but you can't get them on all phones or calls. The AMR family has a bunch of codecs, and a big part of your voice quality depends on which one your phone uses. AMR-NB (narrowband), the simplest, is supported even by 2G networks and is optimized for sounds from 300 to 3400Hz. That includes most human speech, but it tends to make "s" and "t" sounds muddy rather than crisp. AMR-NB can also be implemented at different bit rates, which affects voice quality.
AMR-WB (wideband), which became branded as HD Voice, uses more computing power and gives you your sibilance back by increasing the optimized range to 50 to 7000Hz. AT&T and T-Mobile implemented that on their LTE networks. Most recently, the new EVS (enhanced voice services) codec covers sounds up to 14000Hz, according to its creators.
T-Mobile has HD Voice on its 3G network, but it's slowly turning that network down. Stick with LTE.
Verizon's 3G network uses an older CDMA codec called EVRC-B, which has the same issues we described with AMR-NB. Sprint's 2G/3G voice network uses a CDMA codec called EVRC-NW, which sounds a lot like AT&T and T-Mobile's AMR-WB, except for Wi-Fi calling, where Sprint just uses AMR-WB. Verizon switched to AMR-WB/HD Voice with its new LTE-based "advanced calling" function.
T-Mobile and Verizon also currently support EVS on some phones, although T-Mobile's VP of engineering services Grant Castle described that new codec as only, "minor voice enhancements on top of the normal AMR wideband technology."
Verizon's network VP Mike Haberman agreed. "Music sounds better on it, but is voice really going to sound that different? We really have not seen that. It's nice to say you're evolving, but it's not going to be something that changes the game."
The creators of EVS disagree, of course. In a presentation made for the Audio Engineering Society (slideshow) in 2016, they claim a noticeable jump in audience rating scores from AMR-WB to EVS-WB, the codec that T-Mobile and Verizon are using (the slide below is from that presentation).
Castle and Haberman may be right, though, in that the difference between EVS and HD Voice sounds much less different than the change between AMR-NB/EVRC-B and HD Voice—that's because you get all of your "s" and "t" sounds at the HD Voice level. Listen for yourself.
T-Mobile Codec Comparison
- T-Mobile to T-Mobile EVS LTE Call
- T-Mobile to T-Mobile HD Voice LTE Call
- T-Mobile to T-Mobile HD Voice 3G Call
- T-Mobile to T-Mobile Narrowband 2G Call
To get HD Voice on all of our calls, we need interoperability.
What It All Sounds Like
All four major carriers have HD Voice on calls within the carrier right now. If you are calling someone else on the same carrier and you both have recent phones, you're probably getting HD voice calling. When you make the call, you should see a little HD icon light up in the upper left hand corner of your screen. If you aren't getting HD calling, and you're on Verizon, make sure that both phones have Advanced Calling turned on in settings.
The call samples below were all recorded on calls between two Samsung Galaxy S8 or S9 phones. We recorded the audio by piping a 3.5mm cable into the phone's headphone jack and recording it on a PC using Audacity.
|Listen to HD Voice Calls|
Castle explained that even if AT&T, T-Mobile, and Verizon are all using AMR-WB, the carriers are linked "over an old type of connection which downgrades the voice to narrowband quality." Once the networks upgrade their interconnections, they'll be able to connect VoLTE (voice over LTE) calls to each other in HD quality. They've been promising that this will happen since late 2014.
The situation may get better by the end of 2018. T-Mobile says it's hoping to have HD voice interoperability with both Verizon and AT&T this year. Sprint needs to launch standards-based VoLTE to join the interoperability party, and its CTO John Saw said at Mobile World Congress that would probably happen by the end of this year.
|Listen to Non-HD Voice Calls|
|AT&T to Sprint||AT&T to T-Mobile||AT&T to Verizon/AT&T (HD)||AT&T to Landline|
|Sprint to AT&T||Sprint to T-Mobile||Sprint to Verizon||Sprint to Landline|
|T-Mobile to AT&T||T-Mobile to Sprint||T-Mobile to Verizon||T-Mobile to Landline|
|Verizon to AT&T/Verizon (HD)||Verizon to Sprint||Verizon to T-Mobile||Verizon to Landline|
For cellular to landline calls, anything goes. What we now think of as landlines are now mostly a mishmash of different voice-over-IP systems. They're mostly based on standards called IMS and SIP, but the devil's in the details. Castle said that T-Mobile is upgrading its interconnections for landlines it controls, like its voicemail system and customer care department. For any other cross-carrier call, you'll probably end up dropping to muddy old narrowband sound, with a transcoder potentially introducing latency into the call.
"When you make these calls and they go out to a long-distance connection or to another public switched telephone network, you're going to get downgraded to a narrowband solution…the interconnect work has to be done," Castle said.
Do you subscribe to one of the smaller, virtual carriers that use the major carrier networks, like Consumer Cellular or Straight Talk? The ones that are wholly owned by major carriers, Cricket (AT&T), MetroPCS (T-Mobile), and Virgin and Boost (Sprint), have the same attributes as their parent carriers, including HD Voice calls to their mainline carrier brands. As for the rest of them, some have access to HD Voice, and some don't, an AT&T spokesperson said.
How about those common problems you hear on cellular calls? Generally muddy sound, as you hear in our samples, often comes from transcoding down to a lower-quality codec. Patchy or choppy calls usually reflect a network problem that happened in call setup, Ryan Sullivan, Sprint's VP of product engineering said. That annoying bug where you hear an echo of your own voice? That might be a breakdown in transcoding between two different systems. A computery tone comes from error-correcting bit errors in transmission. That can either be a network issue, or a noise cancellation algorithm straining too hard.
"Generally speaking, based on our experience, the number one cause of less-than-quality audio reception or voice reception is going to have to do with the network connection," Sullivan said.
Why haven't the carriers straightened this out? They say it's difficult and blame each other, but I think it's because there just isn't a lot of money in voice calling any more. Voice calling is the base-level service that people pay for data on top of. Profit-seeking carriers want to sell more data and more devices, rather than root around in the guts of their networks negotiating with other carriers to improve their penny-ante voice services.
At their best, phone calls made over Wi-Fi sound just like calls made over the cellular network. The Wi-Fi calling technology that all the US carriers use essentially encapsulates a voice-over-LTE call, and sends it over Wi-Fi.
That's a best case scenario, though. Unlike LTE networks, Wi-Fi has no way to prioritize voice calls over other traffic. So while your voice call will get bumped ahead of any other business with an LTE signal, on a crowded Wi-Fi network, it just has to wait its turn.
"Depending on the Wi-Fi at your house, you're at the mercy of it. If somebody's playing a game, or what have you [on the Wi-Fi], that will have an impact," Haberman said.
That results in more dropouts, more bit errors, and more dropped calls than you get on cellular, simply because Wi-Fi network quality can vary so much moment to moment. Video streaming apps deal with that inconsistency by buffering content well in advance, but of course, you can't do that with live calls.
The only carrier to face this problem head-on, so far, has been Republic Wireless. Its "bonded calling" technology simultaneously sends call data packets over LTE and Wi-Fi networks, patching them together in places where Wi-Fi starts to fail.
Not many flip phones support VoLTE and HD Voice. The Kyocera Cadence LTE for Verizon does.
How to Make Your Calls Sound Better
Your choice of phone can definitely affect your voice call quality.
First, remember that to get top-quality calls, HD Voice needs to be supported on both ends. Even if you have the newest smartphone, if you primarily call your grandparents who use an old 2G flip phone, you're going to be calling narrowband. Remember, this is what the fanciest phone sounds like when the phone on the other end is 2G.
Both phones should support HD Voice and VoLTE (unless you're on Sprint.) A lot of simpler phones don't, especially non-LTE-capable Verizon voice-only phones. Our roundup of simple phones takes a look at the relatively thin lineup of LTE-capable voice phones out there right now.
On T-Mobile and Verizon, a call between two EVS-compatible phones will offer the ultimate in voice quality. On T-Mobile, these phones should have EVS:
- Samsung Galaxy S7 and later flagships
- LG G5 and later flagships
- Apple iPhone 8 and later
- LG Aristo, Aristo 2, K20 Plus, and Stylo 3 Plus
- Moto Z2 Force Edition
- T-Mobile REVVL and REVVL Plus
- HTC U11 Life
- ZTE Blade Z Max
- Alcatel A30 Fierce
Verizon, meanwhile, verified these phones for EVS:
- Samsung Galaxy S8 and later flagships
- LG V20, G6, and V30
- Google Pixel 2 and Pixel 2 XL
The clearer your signal, the better your voice calls will sound. Carriers have been adding new LTE bands and band combinations over the past four years, and the more your phone supports, the better chance you have of locking in a clear call over VoLTE.
Among phones that support the latest tech, there's still some variation in earpiece maximum volume and distortion at top volume. If you use the speakerphone a lot, speakerphones vary wildly: Rear-facing ones often sound muffled when they're placed down on a table, making front or bottom-facing speakers a better bet.
If you use a Bluetooth headset, the headset may be choking down your voice quality. For a headset to make a wideband call, both the headset and the phone need to support the Bluetooth HFP 1.6 profile. That came about in 2014, but there are still many older Bluetooth headsets (and phones) on the market.
Going Over the Top
If your friends or loved ones are on a different carrier, and you aren't satisfied with the voice quality, you might want to go over the top. "Over the top" services such as FaceTime, Hangouts, Skype, and Whatsapp, are ways of making phone calls without using your carrier's standard voice calling technology.
Apple's FaceTime Audio uses the AAC-HE codec at 16KHz to make voice calls. That produces a quality that's as good, or better, than carrier HD Voice. It works across all current iPhone models, on every carrier, so it's a great way to hack higher quality voice into your world if you live amongst iPhone folks.
Skype and Whatsapp use variants of Skype's SILK codec. Whatsapp runs at 16kHz, and Skype varies. Once again, these are HD Voice-quality codecs, so you'll get better call quality than on an inter-carrier voice call.
The only problem there is that by going over the top, you lose your carrier's voice call quality of service guarantee. So you might see problems like in Wi-Fi calling, such as stalls or dropouts when you're in a congested area and your packets are stuck behind someone else's. Still, though, this puts your call quality back in your own hands while the carriers slowly knit their networks together.