1st generation Active Noise Cancellation
Active noise cancellation started to appear on headphones around 2014, initially the challenge was just getting some sort of effective external noise reduction, cutting out the ambient noises that were getting past the isolation of the headphone earcup & interfering with the audio being produced by the actual headphones.
All ANC headphones rely on a decent seal being provided by the earcup material, and a closed back design to the actual earcup itself. This allows a decent amount of physical isolation from ambient noise which cuts back a lot of the higher frequencies, but does allow most of the lower frequency ambient noise to pass straight through.
Using microphones (typically 1 on each earcup) the ambient noise is monitored by circuitry inside the headphones, and the exact same sounds (same frequency / same amplitude) are generated & played alongside the incoming audio stream – but 180 degrees out of phase. If processed quickly enough, this ‘anti-sound’ effectively cancels out the ability to hear any of the external ambient noise & just leaves the desired audio mostly free of any interference, with just a slight impact on the actual sounds being played through the headphones.
All 1st generation ANC has a delay of a few milli seconds due to processing the incoming audio & generating the anti-sound, which is normally fast enough to not be noticed by the human ear.
1st generation ANC normally focuses on a wide range of frequencies, and can be characterised by the almost cathedral like silence exhibited by some of the early models from Bose. Whilst clearly effective in reducing ambient noises, this can also have the unwanted side effect of a feeling of ‘pressure’ when listening for extended periods which some people are more sensitive to than others. Also due to the wide range of incoming frequencies being cancelled out by anti-sound, the intended audio stream is slightly impacted with some of the audio being unintentionally removed by the process.
This type of active noise cancellation is a bit of a ‘broad brush’ approach, applying the noise cancellation algorithm across a wide range of the audio spectrum indiscriminately. Whilst it can be extremely effective at reducing ambient noise, it does have a slight negative effect on the primary audio stream.
Probably the most well known of the 1st generation ANC style headphones would be the Bose QuietComfort 35.
2nd generation Active Noise Cancellation
From early 2016, advancements were made in several areas & collectively we would refer to these improvements as ‘2nd generation ANC’.
The number of microphones being used to monitor ambient noise increased from 2 to 4 which improved the ability to detect noise from all around the headphones, and the circuitry inside the headphones increased in speed, reducing the time delay to generate the anti-sound.
Ambient noise generally falls into several distinct types, which each have their own distinctive frequency ranges, for example airplane travel has a low frequency rumble which should be focussed on, whereas office noise has a more mid to high range element.
The 2nd generation headphones have multiple modes of active noise cancellation, each of which specialise in the actual type of environment & tailor the noise cancellation profile to suit. So, when travelling on a plane you may select profile1 which would be focussed on removing the background engine noise so boosting the noise cancellation in the lower frequencies, but leaving the rest of the audio spectrum at a normal level. Similarly, a ‘busy office’ mode would reduce the mid range frequencies where conversation occurs more than normal, but leave the low & high frequency range alone.
When compared to the profile of a 1st generation headphone, this tends to apply less noise cancellation in the areas that are not needed which leaves the underlying audio stream less affected by the ANC, but successfully remove more of the background ambient noise than an earlier version of ANC. As the overall level of noise reduction applied to the audio stream is more delicate & focussed, there tends to be much less ‘pressure’ being reported by users of 2nd generation ANC headphones when compared with earlier models.
So – better noise reduction, and less impact on the intended music being played.
As of early 2017, this mode switching of the ANC is performed manually by a switch on the side of the headphone earcup, with most of the newer models offering 2 or 3 distinct modes of noise cancellation.
The very latest headphones are also featuring intelligent features to overcome the practical downsides of wearing noise cancelling headphones – such as needing to remove the headphones in order to have a brief conversation / hear some important announcement etc.
Intuitive proximity sensors which can turn down the music, and switch the microphones into an ambient noise boosting mode in one motion do away with the need to remove the headphones – a great feature in our opinion. Just touching your hand to the headphones to hear what is going on around you soon becomes very natural. As soon as your hand is removed, the active noise cancellation is switched back on & the volume of your music jumps straight back to where it was originally.
Going forwards into late 2017 / 2018, we would love to see the next generation of active noise cancellation offering even more of these profiles, but without the need for the headphone wearer to click a switch in order to change the mode. If the headphone itself could monitor the ambient noise & just apply an intelligent filter that would be fantastic!
I hope you found this guide useful, if you are interested in hearing more about the different types of bluetooth protocol that are being used in wireless headphones & how to get the best sound, please check out our other guide.