Why Noise Cancelling Headphones Don’t Block Voices and What You Can Do About it

Why noise cancelling headphones don't block voices

Many people get expensive noise cancelling headphones in the hope that they will somehow completely shield them from environmental noise.

But when they switch on their headphones’ noise cancelling without music, they notice that all that chatter, shouting and screaming is still coming through.

It may appear at times as if voices are even amplified.

Perhaps you are now sitting in an open office or on a plane and wondering, “Why the heck do my $300+ Bose or Sony noise cancelling headphones let all these conversations right through?”

The reason for this is quite simple:

Current active noise cancelling technology works best for frequencies below 500 Hz and is somewhat effective only up to about 1000 Hz.

Engine noise and traffic rumble are mostly below 500 Hz and so are greatly reduced or even completely eliminated through active noise cancelling (ANC).

The important frequency range for understanding human speech, however, only starts at around 500 Hz. The most important bands for speech intelligibility are 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz.

Bummer: Current ANC does not help above 1000 Hz.

This applies even to highly regarded noise cancelling headphones, such as the Bose QC25 and QC35, and the Sony WH-1000XM3.

Not convinced?

Just look at graphs comparing noise cancelling versus passive isolation for the top noise cancelling headphones.

Examples:

Brent Butterworth’s measurements for the Bose QC25, with ANC on and off on. (see graph Measurements: Isolation)

Rting’s measurements for the Sony WH-1000XM3 with ANC on and off

Note that these graphs aren’t directly comparable as different equipment and methods are being used, but they illustrate the difference between noise cancelling turned on and off.

From 1000 Hz, noise reduction with ANC turned on is no better than attenuation with ANC turned off. In some instances it is even worse.

It isn’t that these companies want to let the chatter and screaming babies pass through. Current ANC technology just doesn’t work for this.

But, in addition to actively cancelling lower-frequency noise, newer ANC headphones also work quite well as noise-isolating headphones.

The ear cups’ seal and isolation substantially attenuates voices and other higher-pitched noise.

For speech blocking, active noise cancelling headphones rely mostly on passive sound isolation, not on their electronics.

With current top-of-the-line noise cancelling headphones, you can expect between 15 and 25 dB noise reduction from 500 to 2000 Hz, which is substantial but not nearly enough to eliminate speech.

Good industrial earmuffs, foam earplugs and noise-isolating in-ear earphones generally work better for reducing speech noise. They are optimized for passive noise isolation.

As far as earmuffs are concerned, you need to put up with less comfort and a higher clamping force though, and with in-ears you need to stick something in your ear.

If you value long-term wearing comfort and don’t want to have something in your ears, active noise cancelling headphones are still a great tool for offices and cafés. They just need a little help.

What can you do to improve the speech blocking performance of noise cancelling headphones?

Normal conversations overheard at close range can easily reach 50 dBA with peaks of 75 dB.

This is way beyond what the passive noise isolation of even the best noise-isolating headphones can cope with.

In the previous section I stated that active noise cancelling headphones are not very good at blocking speech.

They are, however, very good at cancelling low frequency-noise, including the bass of music.

Over the years I have found that lower-pitched noises—even in the absence of chatter—raise my stress levels. Low-frequency noise is more insidious than shouting and laughter, but it does grind me down over time.

This is the noise spectrum in my favorite coffee shop just now at 3 pm:

noise spectrum in a coffee shop

This spectrum is the result of chatter, a couple of AC compressors, coffee makers, and music.

Most offices and coffee shops contain a mix of disturbing sounds.

These sounds include low-frequency noise for which noise cancellers are very good and higher-pitched noises—conversations, keyboard clicking, people chewing ice cubes—for which these headphones need help.

This help is readily available in the form of noise masking with white noise and water streams. Noise masking essentially means drowning out offending noises by overlaying them with a more constant noise.

When people chat, chew, or handle paper bags in a quiet library, you would likely find this extremely annoying. Now picture the same people doing the same thing close to the Niagara Falls. Chances are you wouldn’t even notice them.

To effectively mask speech without turning up the volume too much, we need to shape our white noise to emphasize the speech frequencies and other annoying background noise.

The white noise generator in myNoise is highly flexible and allows us to do just that.

It features 10 different sliders, with which you can adjust the noise for the 10 octave bands of 31, 63, 125, 250, 500, 1000, 2000, 4000, 8000, and 16000 Hz.

The most important speech frequency bands are 500, 1000, 2000, and 4000 Hz.

With the Bose QC35 noise cancelling headphones an effective speech blocking preset for the coffee shop I am currently in looks like this:

Bose noise cancelling headphones speech blocker

(Annotated screenshot from the iOS app. You could also start experimenting with the web app at myNoise.net)

I almost need no masking noise at the low and high frequency bands but I add a little because it makes the masking sound more pleasant.

Note how I have increased the volume for 500 (5th slider from the left), 1000, 2000, and 4000 Hz.

Tip: If these settings don’t quite work, I  usually only need to further increase the volume of the 1000 and 2000 Hz bands.

How do you get there for your noise environment?

One way is to start with the pink noise preset (all sliders set to the same volume). Increase the master volume until you can’t hear the chatter (or whatever else may be annoying you) anymore:

myNoise pink noise preset

Now the chatter is likely gone, but the pink noise might be too loud for comfort.

Decrease the volume of the three left-most sliders and the two right-most sliders by as much as possible while maintaining your masking noise’s speech blocking effectiveness. You could probably set them to zero.

Adjust the other sliders to fine tune your masking sound for comfort. I mostly end up with a triangle with a peak at 1000 Hz.

The web app myNoise.net also has a speech blocking preset which can be used as a base. IMO that preset works better for normal headphones though: normal headphones, because they don’t cancel noise, need a substantial amount of masking noise in the low-frequency range, i.e. the four left-most sliders.

If you haven’t yet purchased ANC headphones, you might wonder whether you should rather get earmuffs, noise-isolating in-ears or even earplugs.

Wouldn’t these be a much better choice?

This depends on your budget, your applications, your desire for comfort, and whether it is acceptable for you to plug your ears.

If you are traveling a lot on airplanes, IMO good noise cancelling headphones are the way to go. They were designed to get rid of turbine noise and do it better than everything else I know of. The same applies if you feel tortured by sub-woofers, rumbling trucks, generators, and other machines that emit substantial amounts of low-frequency noise.

Please note that noise cancelling headphones may not be used as hearing protectors unless they have a noise reduction rating (NRR)!

Tip: To get rid of loud chatter and screaming babies on airplanes, I wear foam earplugs underneath my headphones. I add some white noise and drift away.

Good industrial earmuffs, such as the 3M Peltor X5A are better at blocking speech.

But they are bulky and less comfortable. To achieve their superior noise isolation, they need to exert a higher clamping force than normal headphones. What’s more, even they won’t completely block loud speech, so at times you would have to wear earbuds underneath and play white noise.

Some earmuffs, such as the Howard Leight Sync feature built-in speakers. These earmuff headphones are indeed a good budget alternative to noise cancelling headphones if you want to block conversations and everyday noise. They are a lot cheaper and at least as effective for speech. But they are less comfortable and don’t sound as good. So you are trading comfort for money and vice versa.

Foam earplugs are also better at reducing speech noise, but because of bone conducted sound even these cannot completely block louder voices and you can’t play a masking sound.

Good noise-isolating earphones, such as Shure and Etymotic Research’s in-ear monitors are indeed an alternative. If they fit well (!) and you insert them deeply, they reduce noise, including speech very well. You would again use white noise to mask what is left of the noise. The downside is that you need to stick something in your ear.

Conclusion

Personally, I often wear earplugs or earbuds at night and earbuds in the gym, so I’d like to keep my ears unplugged for the rest of the day. When I need everyday noise blocking, I mostly alternate between noise cancelling headphones and earmuffs.

I love the comfort of noise cancelling headphones and their ability to reduce low-frequency noise, which I find highly stressful.

When I need to focus I don’t want conversations around me either. Many active noise cancellers have pretty good passive noise isolation these days, but it is not nearly enough for louder offices and cafes.  Consequently I mask the chatter with fine-tuned white noise.


Notes:

  • Image credits: geese-gänseschar, by ulleo via Pixabay.com

 

6 Comments
  1. This is a really great article! Thank you for looking into this properly and sharing your findings and tips in this article. Greatly appreciated 🙂

    • Hello Robert,

      thank you very much for your encouraging feedback.

      Looking at the graphs, these noise cancelling headphones are actually already pretty good at passive isolation as well. But there is room for improvement in the mid-frequency range. I am not sure how that would affect wearing comfort though.

      Have a wonderful day.

  2. This is the most thorough article I have read on noise and what may and may not work. I have read hundreds!

    It would give me confidence to make a purchase if you could tell me my best option. I have a new home near a busy road, have hung sound dampening curtains and planted trees. It is the low frequency truck noise that drives me crazy. I looked at noise canceling headphones but am unsure in reading about them whether I can put them on, be in silence as opposed to music and have that lower vibration sound, deadened. I am a writer and just crave silence! Can you advise me?

    Thank you. Thank you. Thank you.

    • Hello Sher,

      thank you very much for the praise.

      I can relate to your pain.

      Before I go into the headphones:
      Does your house have sound-proof windows? If not, perhaps look into that as well. They can make a substantial difference with traffic noise.

      Regarding noise cancelling headphones:
      I currently use the Bose QC35 and I am very happy with their performance against low-frequency traffic noise, even without playing music.

      I have a mix of cars, pickups, medium-sized trucks and city buses. Occasionally a large truck passes by.

      Without music, I still hear traffic noise (reduced) with my balcony door open, but the low frequency booming and rumbling is almost completely gone. If I should assign a number, I would say about 90%.

      Some peaks still come through, but the headphones make a huge difference for me.

      Please note: vibrations you feel can’t be cancelled by headphones and sound also gets conducted through your skull, so there is a limit.

      I have compared the Bose to the Sony WH1000XM3 (their main competitor) against a sub-woofer bass, and chatter (but not traffic noise).

      With speech, the Sony were slightly better, but the difference was small.

      With the bass, it felt like a draw: both reduced the subwoofer substantially, to the point that I felt the sound more in the chest than hearing it.

      I also found both comfortable; here the Bose had a slight edge.

      For my use cases, I prefer the Bose: The WH1000XM3’s sound is too bass-heavy for me and I can’t use them with two devices at the same time (which I do a lot). If you like an emphasized bass, you might like the Sony.

      In any case, both are great noise cancelling headphones; I am not aware of any better ones.

      So my take is this: Pick either the Bose QC35 II or the Sony WH1000XM3 and try them against the trucks.

      With both you have a good chance of substantial relief. See to it that you can return the headphones in case it doesn’t work out.

      While it takes away from the comfort and music wouldn’t sound very good, you can even wear foam earplugs underneath. This helps quite a bit with the higher-bass and lower-mid frequencies and will further reduce the overall traffic noise level.

      All the best.

  3. How about playing white noise through speakers, outside of noise cancelling headphones?
    I’m thinking it could mask some external noise through acoustic interference, and then get a bit filtered by ANC – is it a silly idea?

    • Hello Doubleu,

      Playing masking noise through speakers is, for example, being done in open office environments and hospitals. Several companies offer such sound masking systems with multiple speakers mounted in the ceiling.

      But sound masking doesn’t work through destructive acoustic interference / cancelling of sound waves.

      It actually increases the noise level, but decreases the noise variability in the room and makes conversations that are taking place further away unintelligible.

      The masking noise “drowns out” offending noises. Complete masking is not even necessary for many purposes.
      A decreased noise variability can already improve sleep (it reduces the number of arousals) and ability to focus.

      Any partial cancelling of sounds/destructive acoustic interference through a masking noise in such an environment (if any) would be incidental and would be highly dependent on the position of the listener.

      What kind of noise do you want to get rid of and where is the noise source located?

      You are probably aware of this: active noise cancelling headphones work through acoustic interference. The headphones try to produce 180-degree out-of-phase counter waves to destructively interfere with (=cancel) intruding sound waves.

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