We've all heard the story before. A brand new, very popular device rolls out to the public and everybody hurries to get their hands on it. Shortly thereafter, people start to notice some of the more serious issues that degrade the experience or even make the gadget unusable. When that device is a phone and one of those issues is audio quality during calls and recordings, people can become justifiably angry. It seems this is exactly what's happening with quite a few Nexus 5 owners, as audio going into the built-in microphone is plagued by hissing, popping, loud static, and very low volume.
Like many of the Bug Watches lately, the symptoms aren't completely consistent for everybody. In fact, it's likely that we're talking about a few separate issues that might be playing off of each other, so not all handsets will be affected in quite the same way. Simply put, phone calls and many applications on the Nexus 5 are getting extremely low quality audio. Most people became suspicious when an app like SoundHound is unable to recognize music or Google Now can't understand clearly spoken commands. During phone calls, many of the people affected by this issue are told that they sound like the phone might be really far away or that their voices sound garbled, perhaps even cutting out. When audio or video is recorded on the Nexus 5, the results can often be really uneven, filled with static or hissing, or just not loud enough to hear.
The issues seem to affect phone calls and recordings in almost all reported cases. It's likely most regular apps are also affected, but the degree may not always be enough to interrupt normal function. Strangely, there are very mixed results when the speakerphone is used or calls are made with VoIP apps, suggesting that these things might be accessing sound in ways that don't invoke the issue.
Check out the videos below for sample recordings from some affected devices. Warning, the static-filled video on the left is particularly loud while the hissing video on the right is fairly quiet, be sure to adjust your volume accordingly.
Left: Heavy static, Right: Noticeable hissing
So far, the source of these problems is still a bit uncertain, but it seems the noise cancelling software may be largely to blame. Applications that allow you to make recordings without the built-in noise cancelling feature seem to produce very clear audio without any of the symptoms described above. However, this can leave the recordings prone to some echoing and background noise, which is to be expected when noise cancelling is disabled. This is reminiscent to an issue where some VoIP clients on the Nexus 4 suffered poor audio quality because they were unable to access audio filtered by noise cancellation.
Some people have theorized that one or both of the microphones in some Nexus 5 units could be faulty or the sound may be obstructed by glue from the manufacturing process. If this is true, it's possible that the noise cancellation algorithm is having trouble getting enough sound to determine what audio is coming from the background versus what should be kept. This is certainly possible without blaming hardware issues, but physical defects would help to explain why some units seem to function very well while others are virtually unusable.
Unfortunately, there's no absolute fix for this yet, but that doesn't mean an affected Nexus 5 can't be used successfully as a phone. If you prefer a MacGyver-like solution, a few people have had marked improvement by simply covering up the secondary microphone on top of the handset. While this has worked for a few people, most aren't haven't much luck with it, and it's not the most elegant solution.
The more obvious option for making calls is to resort to using a Bluetooth or wired headset, or relying on the speakerphone. The hands-free alternatives are either completely without noise-cancelling features or they implement their own, so the phone won't modify the audio it receives from them. The speakerphone still shows issues for some people, but it might be a handy fallback if it works for you. Of course, this only really solves the issue with making good phone calls, but it leaves you high-and-dry for making recordings or using most other audio-dependent apps. Oh yeah, and there are some issues with in-line (wired) headsets, but we'll get to that in an upcoming Bug Watch.
I'm sorry to say I don't have a lot of good news regarding this issue, at least not yet. There are people saying Google reps are acknowledging issues over the phone, but it's still a bit hit-and-miss. One of the two threads covering these issues has a few responses from Paul, a well known Google Community Representative, stating that this is a known issue but its status is still undetermined.
Given that complaints began just a couple of days after the first deliveries of the Nexus 5, some people are becoming nervous that the problem may not be exclusive to software and that there may be a hardware defect involved. As a result, a few owners have started returning their handsets or requesting exchanges, hoping to receive a more functional replacement. At this point, there's not enough information to make any recommendations, but it may be worth starting a conversation with Google's support if your device is affected.
Hopefully this issue can be resolved with a software-based fix, much like many of the 2013 Nexus 7s were (eventually). Until then, keep a close eye on this issue and we'll keep people updated as we learn more.