Sound Masking

Masking Is Not Blocking, and the Difference Decides Everything

There are only two ways to stop a sound from bothering you. Most disappointment here comes from using one while expecting the other.

Blocking reduces what reaches you. Thicker windows, a solid door, a seal along the bottom of it, earplugs. Less sound reaches your ear than before. This is the obvious approach, and people try it first. But it costs money and effort, and it works worst exactly where household noise is worst: deep sounds, which pass through walls, floors and windows much more easily than high ones.

Masking adds a steady sound. The unwanted noise arrives just as before. What changes is the background around it, which you make louder on purpose. The room ends up with more sound in it, not less. Yet the noise you cared about stops registering.

Put plainly, that sounds like a trick. It is not. It works because of how your hearing decides what counts as an event.

The Ear Compares, It Does Not Measure

A sound meter measures how loud a sound is. Your hearing does not work like that. What you notice, and what wakes you, depends more on contrast: how far does this sound stand out from what was already there?

A creaking floorboard in a silent room is an event. The same creak, at the same loudness, in a room with a steady background sound is nothing at all. The creak did not change. It just no longer stands out from what is around it. Your hearing is built to notice changes, not to keep track of loudness, so it has nothing to report.

This is why masking works at all. It is also why the next rule exists. Your hearing does not make this comparison across all pitches at once. It makes it in narrow pitch ranges, one at a time, and only sound in the same range takes part.

Masking Works by Pitch, Which Is Why Colour Matters

The inner ear works like a row of many small detectors, each tuned to a narrow range of pitch. The comparison that decides whether you notice something happens inside each of these ranges, not across all sound at once.

This leads to the most useful point on this page. Only the part of your masking sound that is close in pitch to the unwanted noise does any work. The rest does not help. It is not harmless either: it is extra sound in the room, and extra sound you hear all night, for nothing.

Play white noise against a lorry passing outside, and most of the sound you make is far higher than the lorry, where there was never a problem. The small part that overlaps does all the work, so you turn it up, which mostly adds hiss. Play brown noise against the same lorry, and its sound is stacked where the lorry is, so a much lower volume covers it. Neither colour is better or worse. One matched and one did not.

One more thing is worth knowing. A masking sound reaches up in pitch much more easily than down. A deep sound covers a good range of sounds above it. A high sound does very little for sounds below it. This is why brown noise is the safer choice when you are not sure: it reaches up. It is also why a bright, hissy noise is almost useless against rumble, however loud you make it.

Which Colour for Which Noise

Match the sound to the problem. The player at the top of this page has four colours, so you can settle this in a few minutes against the noise you actually have, instead of reading about it.

Deep noises: use brown. Road and rail traffic, aircraft, machinery, a boiler, a washing machine, bass through a floor or ceiling, footsteps from above, and a snoring partner. This is the biggest group in ordinary homes, because deep sounds are exactly the ones that walls and floors fail to stop.

Speech: use white or green. Talking through a wall, a television next door, an open-plan office, a housemate on a call. The parts of speech that let you understand words sit mostly in the middle and upper-middle range, where white noise is strong and brown noise is much weaker. Green puts its sound in the middle of that range. It is often more comfortable for the same effect, because it does not have white noise's harsh top end.

Mixed or unknown: start with pink. Pink sits between the two. It is a sensible first try when the noise varies or you have not worked out what it is. Most people also find it the most natural-sounding of the four, which matters over eight hours.

Sharp, sudden, high sounds: masking will struggle. A dropped plate, a slammed door, a dog. The section on limits below covers these. The honest answer is that a steady masking sound handles them poorly, and it is better to know that in advance than to decide the method has failed.

Tinnitus is a different problem and does not belong on this list, because the sound does not come from outside and the aim is not the same. It has its own page, with a more honest account of the evidence than you usually find on this subject.

Set the Volume Against the Noise, Not Against Silence

After choosing the wrong colour, the most common mistake is choosing the right one and then playing it far too loud.

Aim for just above the noise. As soon as the noise stops standing out, masking has done its whole job, and any extra volume is wasted. If the colour matches, that point comes at a surprisingly low volume. If you keep turning it up and up, you do not need more. It is a sign that the colour is wrong and you are trying to fix a pitch problem with volume.

Set it for the loudest moments, not the average. Most real noises go up and down. Snoring comes in cycles, and traffic comes one vehicle at a time. A volume that covers the quiet stretches lets every loud moment through, and the loud moments are what wake you. Listen through a few cycles of the noise and set the volume for the loudest part.

Louder works against you. Past a certain point, you have not removed a noise. You have replaced it with one you chose. You also spend eight hours a night at a volume you picked while awake and annoyed, which is not when people judge these things well.

Give it five minutes before you decide. For the first thirty seconds, any masking sound feels like an intrusion, because you are listening to it. Whether it works is a question for minute four, when you have stopped listening.

What Masking Cannot Do

It does not reduce the noise reaching you. This is the important one, and most pages on this subject leave it out. Masking changes whether you notice a sound. It does not change what reaches you, and adding a masking sound means there is more sound in the room, not less. Noise at night can affect your sleep in ways you can measure, even if you do not wake up and do not remember anything in the morning. That is why the World Health Organization's Environmental Noise Guidelines for the European Region strongly recommend keeping road traffic noise below 53 decibels averaged across the day and night, and below 45 decibels at night. These are limits on the noise that reaches you, not on how annoying it is. If that is your situation, masking still makes the night easier and is worth doing. But it does not replace reducing the noise itself.

It handles sudden noise badly. A constant hum is the easy case: the masking sound only has to sit above a level that never changes. A door slamming at random times is the hard case, because a masking sound loud enough to cover the bang is far louder than the rest of the night needs. Sudden sounds are also the ones your hearing is most alert to. A steady masking sound softens them. It does not remove them.

It does not keep playing on a locked phone. Any browser tab, including the generator on this site, stops when your phone pauses it. That happens as soon as the screen locks or you switch apps. Browsers do this to every website. It is not a fault of one page. For masking all night, you need an installed app or a sound machine.

It is not a treatment for anything. Masking is a way of covering a sound. If your sleep has been bad for weeks, or if snoring in your bed comes with gasping or pauses in breathing, the useful next step is a doctor. No colour of noise changes that.

Masking, Earplugs and Noise Cancelling Do Different Jobs

People usually present these three as competing answers to one question. They are not. Each one works on a different range of pitch. Knowing that tells you which one to use, and when to combine two.

Earplugs work worst where household noise is worst. They cut high sounds much better than deep ones. So earplugs deal well with a television and poorly with a lorry or a snore. There is also a hard limit. Sound reaches the inner ear through the bones and tissue of your head, whatever is in your ear, and measurements put that limit at about 40 to 60 decibels (Berger, Kieper & Gauger, 2003). Past that, better earplugs stop helping. The full comparison is here.

Noise cancelling headphones are the exact opposite. They work best on deep sounds and less well on higher ones. That is why they make such a difference on a plane and so little against a conversation. So they work well alongside earplugs, not instead of them. But they need headphones, and most people cannot sleep comfortably in headphones all night.

Masking is the one that works for a whole room and a whole night. It costs nothing, needs nothing in or on your ears, works for two people in a bed instead of one, and is the only one of the three you can match to the pitch of the noise.

The best answer is often two of them. Earplugs plus brown noise work well together because their weak spots do not overlap: the earplugs take out the high sounds, and brown noise covers the deep sounds that get past them. This site sells neither earplugs nor headphones, so there is no reason to pretend one wins.

If You Only Read One Paragraph

Masking does not reduce the sound reaching you. It raises the background so the noise no longer stands out, and your hearing reacts to that contrast, not to loudness. Because your ear compares sounds within narrow pitch ranges, only the part of your masking sound that is close in pitch to the noise does any work. So choose the colour first and the volume second. Brown for traffic, machinery, bass and snoring. White or green for speech. Pink when you are not sure. Set the volume just above the loudest moments of the noise, and no higher. Masking will not lower the noise reaching you, will not handle sudden sounds well, and is not a treatment for anything.

Frequently Asked Questions

Related pages

• Noise Colour Test — Two questions and a listening test to find your noise colour.
• Decibel Meter — Check how loud your room is, and which noise colour covers it best.
• Block Out Snoring — Snoring is the hardest sound to cover: deep, uneven, and a metre from your head with no wall in the way. What really helps.
• Block Traffic Noise — Your walls already removed the high sounds from the traffic outside. That is why brown noise covers it indoors and white noise does not.
• Masking vs Earplugs — Earplugs work least well on deep sounds, which is most household noise. Masking can be matched to the noise. Why the answer is usually both.
• Brown Noise Machine — Two very different products are sold as a brown noise machine, and one of them cannot make brown noise. What to check before buying.
• Brown Noise — The deepest colour: a steady rumble that is best for traffic noise and long nights.
• White Noise — The flat, bright colour, and the best of the five at making speech impossible to follow.
• Green Noise — The middle colour: pink noise with the middle sounds made stronger, and the only one of the five with no standard definition.
• Pink Noise — The balanced, natural-sounding colour: a good default, and the sound engineers use to test speakers.
• Brown vs White Noise — The two colours furthest apart: what each one can and cannot cover, and why your speaker may decide for you.
• Brown Noise Generator — A real brown noise generator in your browser: made live as you listen, with no file and no loop.
• About — Who publishes this site, how we check what we write, and how we handle health topics.
• Block Neighbour Noise — Bass and footsteps need brown noise. Voices through a wall need white or green. Most advice gives one answer to both.