Noise Masking or Active Noise Cancelling: Together or Alone?

In this post, I’d like to demonstrate how much of a difference noise masking, active noise cancelling, and noise isolation alone and in combination make when it comes to eliminating disturbing nighttime (and daytime) noises.

We are going to listen to a “noisescape” containing large-truck noises and resonances, honking of smaller and larger vehicles, and barking of a large and a medium-sized dog.

I am going to apply three different noise reduction techniques so that you can hear the effect they produce against these disturbing noises.

To truly experience and appreciate the effects of the different technologies, I highly recommend that you wear decent headphones or earbuds while going through this article and listening to the audio.

A phone or computer speaker can’t properly reproduce truck and other street noises!

If you can, listen in an otherwise quiet environment.

Primer on noise masking

Noise masking works by covering distracting or disturbing noises (e.g., snoring, barking, chatter, lip smacking etc.) with a continuous sound (a masking noise) such as white noise or a waterfall or rain sound.

Many people have no problem falling and staying asleep against the backdrop of even heavy rain, but if someone drops a tea spoon on a tiled floor, they wake up.

Intermittent or sudden noises are the ones that disturb us the most at night. They are also the most distracting ones when we want to concentrate.

It is the difference between the sudden “cling” when the spoon hits the floor and the room background noise level that arouses us rather than the absolute volume.

By playing a masking sound (e.g., via your white noise machine, headphones, sleep earbuds, white noise app, etc.), you can raise the background noise level and reduce that difference.

If you play an optimized masking sound loud enough via good headphones/speakers, you can even completely drown out that “cling” (or your spouse’s snoring or a barking dog) so you don’t hear it anymore.

Noise masking and noise isolation at work against street noise, honking, and barking

First, listen to this “concerto” of street noise, trucks, honking, and barking:

Set your headphones to a volume so that the following sound is loud enough to be realistic but still bearable. Imagine yourself in a room close to a road with an open window. That’s the volume you want.

(I use 80% volume in Windows, but I don’t know the maximum output of your computer/phone and headphones vary in their sensitivity.)

Now let’s cover that with a masking noise (optimized to cover the barking and honking frequencies):

As you can hear, the masking noise is already quite loud (as loud as I would go), but the truck rumble, barking, and honking still come through loud and clear.

I tried increasing the masking noise volume by an additional 6 decibels, but this made it way too loud for sleeping or long-time listening!

And while it helped masking the dogs’ barking, the truck noise and honking still disturbed me.

In summary

• Noise masking alone didn’t work well against this street noise because it is too loud!
• The louder the noise you want to mask, the louder you have to play your masking sound. This, unfortunately, limits how much you can do with noise masking alone.
• Beyond a certain volume, even the most pleasant masking sound becomes a nuisance. You may not hear 75-decibel barking anymore but now you are tortured by a waterfall sound played at 85 or 90 decibels.

This is where noise isolation comes in very handy.

Here is the noise reduction you can get from good over-ear noise isolating headphones (without active noise cancellation):

The barking, honking, and street noise sound muffled and their volume is reduced. That’s a lot better, but, at least for me, it is still too loud for sleeping.

And here is the result, if we cover this with our masking noise (same volume as before):

The only thing I can still clearly discern are the truck resonances.

I find this an acceptable result, but the trucks are still bothering me, and the masking sound is a bit too loud for my taste. However, if I was to lower the masking noise volume, the honking would become noticeable again.

Can we get more relief at a lower masking noise volume by adding active noise cancellation?

To be continued after this brief interlude:

How is noise cancelling different from noise masking?

Active noise cancelling headphones/earbuds use built-in microphones to listen to environmental sounds and play an opposing signal (via their speakers) to cancel out these environmental sounds.

Unlike noise masking, which adds noise to mask (=drown out) unwanted sound, noise cancelling reduces the overall noise level your ears are exposed to.

Active noise cancelling (ANC) works best against low frequency noise (<250 Hz) and provides benefits against lower mid frequency noise from 250 up to about 1000 Hz (the cut-off frequency varies with the headphone model).

Against higher mid and high frequency noise, current ANC technology is not yet effective.

In contrast to this, while noise masking can in principle work against all frequencies, it is best-suited against lower mid, mid and high frequency noise.

In a nutshell, noise cancelling and noise masking can complement each other very well!

(Louder masking noises that are low-frequency emphasized can work, but they may exhibit rumble that some people find disturbing all by itself. Moreover, smaller speakers, e.g., those of typical white noise machines, can’t create the low frequencies necessary to mask bass noises.)

It is important to note that ANC always works in concert with passive noise isolation, i.e., the headphones’ ear cups or earbuds’ ear tips also act as a physical sound barrier that reduces incoming noise.

Can’t we use just passive noise isolation together with noise masking?

Passive noise isolation with ear-cups or shallowly-inserted earplugs alone can do well against mid and treble frequencies (so you definitely need well-isolating headphones) but under-performs against low frequency noise (like the street noise you just heard and lower-pitched barks and horns).

There are earplugs and earplug-type headphones without active noise cancellation that work well against low frequency noise.

But, these need to go deep into the ear canal!

I often use completely-inserted foam earplugs, but not everyone can or wants to tolerate this deep seal.

(My most-used tool to get rid of nighttime noise (including barking) is still the combination of foam earplugs and white noise machine.)

Active noise cancelling electronics make you much less dependent on a deep earplug-seal.

Thanks to ANC, people who can only accept headphones can get good to excellent low frequency noise reduction and good performance against lower mid frequency noise without the need to plug their ear deep inside the canal.

Let’s go back to fending off our road noise and hear the effect of ANC:

Active noise cancelling, noise masking, and noise isolation at work against street noise, honking, and barking

Recap: We can use noise masking together with noise isolation to mostly drown out a combination of street noise, honking and barking, but we need to play even a well-optimized masking sound quite loud.

Here is our street noise again with passive noise reduction provided by good noise-isolating headphones:

Now let’s turn on the active noise cancelling function on these headphones (Sony WH-1000XM4):

The truck rumble is now almost gone and the barks of the larger dog are a lot quieter. Higher-pitched noises have come to the forefront.

But they are not really louder as we will see when we mask them (below). It is just that the lower frequencies in the street noise are so effectively reduced that they don’t mask the higher-pitched noises anymore.

(In case you are wondering how much quieter everything is, just play the original street and barking noise above again.)

It’s a world of a difference but the barking and honking aren’t gone yet.

Now let’s combine active noise cancelling and noise masking:

Both the barking and the street noise are gone. The only thing I can still hear is a faint honking towards the end (and only because I am looking for it).

In fact, if it wasn’t for the loud honking, we could have played the masking noise even at a substantially lower volume.

How much did active noise cancelling really help here?

That’s easy to hear.

For comparison, let’s turn off ANC and keep everything else the same, i.e., we rely on the headphones’ noise isolation and use the same masking noise volume as in the previous audio:

Now, some of the street noise, the barking in the background, and the lower-pitched horn can be heard again.

And to drive this point home, here is how much louder I had to play the masking noise to mask the barking and honking when we relied only passive noise reduction (and the result is still not as good):

In summary

• The headphones’ ANC function adds substantially to noise masking and passive noise isolation against both the street noise (mostly low frequencies), the lower-pitched barking (200 to 700 Hz) and large-vehicle honking (peaks at around 500 Hz).
• Even the higher-pitched barking is reduced: it exhibits a first peak at around 600 Hz, against which the ANC is effective.
  

Noise pollutants’ frequencies overview table

In the following table, I have identified some of the loudest “noise pollutants” in the noise sample you have just heard, and which of the applied tools contributed to reducing that noise:

Conclusion and current state of the art

Against many nighttime (and daytime) noises, noise masking, active noise cancelling, and passive noise isolation are synergistic.

This includes street noise, snoring, chatter, barking (larger dogs), honking, music bass, footstep noise, and HVAC systems.

Against higher-pitched crying, crickets, small dogs, and screeching brakes current active noise cancelling technology doesn’t offer much benefit. Good passive noise isolation in combination with an optimized masking noise are what counts.

If you can sleep on your back or need relief during the day, the combination of noise masking and quality over-ear active noise cancelling headphones (e.g., Sony WH-1000XM4) is a very effective tool against the “noisescape” you have just heard in this post.

A select few active noise cancelling earbuds also have a battery that lasts a whole night, but ideally they should be smaller to allow for comfortable side sleeping.

Specialized sleep earbuds with built-in masking sounds, such as Bose’s Sleepbuds, are available. They are very small, designed for side sleeping, and they have ear tips that sit at the ear canal entrance, so they don’t have to go in deep like foam earplugs.

But they and other current noise masking sleep earbuds don’t yet offer active noise cancellation.

This is somewhat surprising because Bose has great active noise cancelling technology in their normal earbuds. Perhaps they haven’t yet figured out how to make them small enough with a battery that can power both noise masking and noise cancelling for a whole night.

I have read the argument that noise cancellation is not effective against intermittent noises, but in my own experience, this is no longer the case with state-of-the-art noise cancelling headphones. Whether ANC helps or not depends much more on the dominant frequencies in the noise you want to eliminate.

Then there are other sleep earbuds, such as QuietOn, that do feature active noise cancelling but unfortunately no noise masking. As we have seen in this post, a customized masking sound is necessary if you want to make louder noises go away.

I don’t want to knock these devices, and, depending on the noise problem that needs solving, they can work just fine.

But, these sleep earbuds would be more powerful and versatile if, in addition to isolating well, they combined both active technologies used in this post:

I’d like to see small sleep earbuds with comfortable ear tips suitable for side sleepers that have customizable (via an EQ) built-in masking sounds and powerful active noise cancellation and an all-night battery.

I am optimistic, we will get there.

For detailed noise reduction tests, please also read the post Active Noise Cancelling vs Noise Isolating Headphones.

The post Wearing Noise Cancelling Headphones over Earplugs details what maximum noise reduction of everyday noise you can get.