Beware, when shopping, that ‘noise
cancelling’ can also (somewhat deviously)
refer to non-active noise cancellation. Some
kind of passive blocking is, as we have
discussed, part of just about every active
system – from silicone or foam earbuds to
the solid closed back of ANC cans – but some
sell these natural baffles alone as a feature.
You’ll generally be able to sell by the price if
something includes an active element.
It is, at least in theory, feasible to run an
ANC system on open-back headphones. The
problem is that a vast amount more filtering
and cancelling needs to be done, over a wide
range of frequencies, since the passive noise
cancelling element so critical to other systems
has been removed. That heavy processing
tends to ruin the quality of the source audio,
so open-back ANC isn’t common.Beware that ‘noise
cancelling’ can also
refer to non-active
noise cancellation
TECH WARS: ANALOGUE VS DIGITAL VS ADAPTIVE
Because there’s more than one way to skin the noise cat
Just as there are three places to put the
microphone in an ANC setup, there are three
ways to do the cancellation itself, and each
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Analogue ANC is the method that seems
to make the most sense, because it removes
latency from the equation. Using an analogue
setup means devices can react instantly to
changes in sound around them, meaning a
theoretically more accurate anti-noise
system. But the engineering required to
create the perfect analogue ANC solution is
astronomical and can be incredibly expensive.
Analogue also drains far less battery than
digital ANC – but digital ticks many moreboxes. Because it generally employs a
sophisticated DSP to do the grunt work, it
gives you far more control over the sound
mix than an analogue system. The
performance of digital devices can also be
changed over time; if you’re sure to keep up
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better algorithms improve the overall
experience. Some digital setups can, however,
add some 30ms lag between the input sound
and the signal to the ear.
That’s where adaptive noise cancelling
comes in. A slightly more advanced (but not
entirely distinct) form of digital ANC, it
adapts its anti-noise signal both to thesurrounding environment and, predictively, to
match the sounds it presumes it will have to
cancel once its latency period has passed.
There’s certainly an argument to be made
that analogue ANC, with its lessened latency,
is the tech that achieves its stated goal best.
But, particularly since adaptive algorithms
have become more commonplace, the digital
variety puts in a strong showing. It’s also far
more common – the vast majority of modern
devices carry a digital package.
Pick the headphones that work for you.
Choose based on style, construction and
substance. Throwing money after the word
‘analogue’ could turn out to be a poor idea.without ruining the sound. And it’s more
expensive than single-mic alternatives.
ANC requires power. While this can be
drawn from a USB or lightning cable, it’s not
possible to supply enough juice through a
3.5mm jack. Given that they already carry a
battery, you’ll more commonly find ANC on
wireless audio devices; if you’re looking at a
wired solution, check to see where that
battery is located. Sometimes, particularly
on older devices, you’ll find it sharing space
with the ANC hardware in an awkward
module mounted on the headphone wire,
which can mess with the balance.
Even if you’re going wireless, bear in
mind that activating the ANC engine will
increase your device’s battery draw, and so
cutting the between-charges lifespan of
Bluetooth headphones.
A better solution, and one which is
becoming increasingly more common (and
effective), is some level of audio passthrough,
often called ‘transparency mode’ or similar.
The presence of passthrough is no guarantee
that it’ll work – we’ve heard some absolute
stinkers in this department, devices which
have turned the sounds of the outside world
into a robotic mess while destroying the
main audio signal – but that’s not the norm.
Recent advancements seem to have ironed
it out. But it’s worth testing the passthrough
functionality before purchasing if you can. If
that’s not possible, we’d highly recommend
looking for something with a number of
levels, so you’ll be able to find a balance thatsuits you. Passthrough is, if anything, a neat
side effect of ANC, using technology that is
already there to add a useful new function to
your headphones.
The final critical element of an ANC setup
is the form factor. Passive noise cancelling is
an essential part of the equation, but how
well is it executed? How much sound will the
foam earpieces of your noise cancelling cans
let leak in? How much baffling can those tiny
true wireless earbuds really perform? This is
something that varies wildly; only when
every element of an ANC device is properly
balanced will it be truly effective.62 T3 MARCH 2020
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