Active noise cancellation sounds (pun intended) great in theory, but its reality is underwhelming if not degrading.
As I mentioned in my prior write-up, my new personal smartphone, the Microsoft Surface Duo, is (more than) a bit clumsy to hold up to my head to take and make phone calls. Plus, the added manipulation time required to use it in this way (not only pulling it out of my pocket but also folding it 360° before pressing “answer”) leads to a higher likelihood of missing incoming calls versus a standard smartphone. Check out the end of this video to see what I mean:
As a result, I’ve been alternately trying out various manufacturers (and models, in some cases) of Bluetooth earbuds, with which you can take a call via a single capacitive or physical switch press without needing to first extract the phone from your pants, satchel, purse, etc. And my testing wasn’t communications-centric; I also evaluated them for music-listening and video-watching purposes. My results have been enlightening: no matter that, they’ve also been largely underwhelming in reinforcing that there’s no getting around the fundamental laws of physics.
Before diving into the details, let’s briefly cover a few fundamentals. Passive noise reduction (PNR, also sometimes referred to as “passive noise isolation”, which I personally prefer, along with my least favorite alternative, the technically inaccurate “passive noise cancellation”) involves leveraging various physical means of preventing ambient sounds from interfering with whatever you’re listening to and audibly communicating with others. A side benefit is that it also often can prevent others around you from hearing what you’re listening to, too.
With conventional headphones, PNR factors include:
With earbuds, which instead fit inside the ear, key factors in PNR effectiveness include:
Finally, for both traditional and earbud-based microphone-inclusive headsets, PNR (specifically as experienced by the person you’re communicating with) is dependent on factors such as:
Speaking of microphones, they play an added important role in the more commonly referenced form of active noise cancellation (ANC, also sometimes referred to as “active noise reduction”), taking place within the headset itself versus within the microphone(s). As Jabra describes it:
Active Noise Cancellation counters noise. It detects and analyzes the pattern of incoming sound, and then generates an “anti-noise” mirror signal to cancel it out. As a result, you experience a drastically reduced level of noise. ANC is optimal for steady, low-frequency sounds, such as ceiling fans, engine noise, or office chatter. You usually find ANC in stereo headsets that cover both ears, but some mono headsets also use it to improve noise management.
There are also multiple methods of implementing ANC, leveraging microphones on the outside of the headphones (seemingly the most common approach, from my anecdotal research), the inside, or both. Jabra again (read their white paper for more details on the implementation and results pros and cons of each approach):
Feedforward active noise cancellation (Mic outside the ear cup)
In a feedforward setup, the microphone is placed outside the ear cup. The mic hears the noise before the person does. ANC then processes the noise and creates the anti-noise before sending the resulting signal to the headset speaker.
Feedback active noise cancellation (Mic inside the ear cup)
In the feedback setup, the mic lives inside the ear cup and in front of the speaker, so it gets to hear the resulting signal in exactly the same way the listener does.
Hybrid active noise cancellation (Mics outside and inside the ear cup)
As you can guess, a hybrid approach takes the best of both worlds, combining feedforward and feedback ANC by placing a microphone on the inside and outside of the ear cup.
And the additional microphones present in an ANC headset design sometimes also find use in implementing features such as so-called “transparency” mode—enabling you to hear the sound of an approaching vehicle, for example, or to converse with your spouse without needing to first take off the headphones or remove the earbuds—and “hear-through”, so that you can more naturally hear the sound of your own voice when on a phone call, Zoom session, etc.
Tutorial over, let’s take a look (listen?) at the alternatives I evaluated. My bases for comparison purposes were two traditional Bluetooth headsets, Microsoft’s first-generation Surface Headphones:
and Sennheiser’s Momentum 2 Wireless:
Both headsets are snug-fitting over-the-ear approaches with pads that robustly implement PNR. Differences between them include the Surface Headphones’ support for multipoint (the ability to simultaneously connect to a smartphone and computer, for example) versus the Momentum 2 Wireless’ support for the high-quality baseline aptX audio codec (that said, high-bitrate variants of SBC aren’t shabby, either, nor is AAC, although the latter reportedly doesn’t play well with Android). But they’re both quite bulky, both to wear and to tote around, therefore explaining my interest in also trying out some comparatively inconspicuous earbuds.
Candidate 1: Jabra’s Elite 75t, which, curiously, didn’t initially support ANR; the company added it via a subsequent firmware update:
#2: Jabra’s Elite 85t, which, versus the Elite 75t, trades off more heft (and a higher price tag) for a hybrid ANR implementation:
#3: Sennheiser’s Momentum True Wireless 2; these differ from the others, as was the case with the earlier-mentioned Momentum 2 Wireless headset, in their support for the aptX codec:
Quick aside: the term “true wireless,” which you’ll also see used by other manufacturers, references that not only the connection between the smartphone (or other broadcasting device) and the headphones, but also the connection between the right and left sides of the headphones, is wireless
Last but not least, #4: Beats (now owned by Apple) Studio Buds, the smallest and lightest of the bunch, albeit with proportionally shorter battery life (since battery payload is a dominant factor in earbud size and weight…that said, all of the earbuds I tested specify markedly shorter battery life when their ANC and related additional audio processing features are enabled):
The results? The biggest surprise (and not in a good way) when listening to music and video soundtracks was the Jabra Elite 85t, whose more advanced ANC implementation—at least on paper—didn’t translate to better ANC results in my ears. Quite the contrary, in fact; they were the worst of the bunch in my “run a vacuum cleaner in close proximity while listening” test (I ended up returning them for a refund). I’ll qualify my comments somewhat by noting that, as mentioned earlier, ANC is notably augmented by effective PNR which, for earbuds, is highly dependent on their “fit.” Conceivably the Elite 85ts’ larger size and heavier weight translated to an inferior “match” with my ears, although my results were reminiscent of those in others’ reviews I subsequently perused. And to that point, I’m surprised that none of the earbuds’ applications included a “fit test” like the one Apple provides for its AirPods Pro earbuds.
The other three earbud options were more-or-less a wash with music and soundtracks, ambient noise reduction-wise, and none of them came close to the conventional Microsoft and Sennheiser headphones with their inherently superior PNR facilities. On the other hand, all of units I evaluated were unacceptable from an ANC perspective (specifically to the person on the other end of the call) when used for telephony purposes. They again did a passable job of blocking the ambient noise which made it to my ears (thereby explaining the earlier-mentioned “hear-through” mode option), but the person on the other end of the call continued to discern any discordant clatter loud and clear. Some owners of Jabra’s earbuds even report that their phone call participants hear an amplified cacophony when ANC is switched on!
This too was a big surprise, and I’m unclear on what the root cause is. Since none of the earbuds or headsets I tested place the microphones on the end of “stalks” (as with Apple’s AirPods line), and since they all use mics with omnidirectional pickup patterns, there was no inherent location-selectivity to what they were sensing. And audio in the voice frequency band is particularly challenging, I realize…how do you differentiate between egregious background noise (including the aforementioned “office chatter” of others’ voices) and the all-important sound of the earbuds owner talking? I also thought that perhaps outgoing audio might be routing through a different circuit-and-software path which (for unknown reasons) wasn’t ANC-enabled, and/or that the added latency of ANC processing might be egregious for real-time communications purposes…but then again, I didn’t discern any loss of lip sync when watching and listening to a movie on any of them, so…
Readers, any insights on why ANC wasn’t working for me with telephony, along with any other thoughts or questions, are as-always welcomed in the comments!
This article was originally published on EDN.
Brian Dipert is Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.