Sound Guys

What is isolation?

Growing up, I was the kid who always had headphones on. Riding the bus, studying, working out: if it wasn’t absolutely necessary for me to be talking to other people, I was listening to music on my giant Koss headphones.

I wore those things everywhere; people made fun of me because they were so big. My parents rolled their eyes and tried to get me to wear smaller, more “fashionable” models, but they always just ended up on my shelf because they never sounded as good. I couldn’t really put into words why I loved those headphones so much then, but I know now the reason is that better isolation most often means better-sounding music.

What are decibels?

When we talk about how powerful sound is, we talk in terms of decibels (dB). The dB scale is logarithmic in nature, so every increase of 10dB represents an increase of force by a power of 10, and an increase of perceived loudness by a factor of 2. 70dB is 10 times as powerful as 60dB, but only twice as “loud.” Similarly, a decrease in 10dB is a halving of loudness, a decrease of 20dB will mean the sound is only 1/4th as loud, and so on.

For reference, most smartphones tend to range between 30dB (at minimum volume) and 110dB (at maximum volume) when you listen to headphones. As you can imagine, this means that increasing volume on your headphones will subject your ears to a lot of force fast, so it’s important to keep your listening volumes low. But how low is safe changes depending on how long you’re listening. If you’re listening to music 8 hours a day like I do (I mean come on, I review headphones), NIOSH recommends you keep your levels below 85dB. However, casual listeners who only listen for 45 minutes or less can feel free to crank their tunes a bit louder.

Your inner ear is a lot more delicate than you might realize: it is extremely easy to damage your hearing with loud music. Our ears are made up of a lot of parts, but we have an exceptionally weak link in the chain: teeny-tiny hairs inside our cochleas. If those tiny hairs bend, break, or fall out, our ears can’t send signals to our brains to interpret as sound. While they do that anyway as we age, they don’t grow back. Ever. Once the damage is done, it’s done.

So if you’re trying to limit your exposure to high levels of noise, there are a few strategies you can employ:

This sounds a little navel-gazey, but if you can avoid loud noises, you should do so. A study in 2012 once concluded that you should listen to your music at under 50% of your smartphone or MP3 player’s volume slider, and that’s a fairly good benchmark. Beyond that you tend to stray into territory where your tunes might be a little too loud with most modern headphones. If you need to crank your tunes up past that, it’s a good idea to figure out what needs to change—unless the problem is a lack of output power.

This is the preferred solution, because there’s no amount of noise reduction that is ever really “too much.” By physically blocking out sound, you make every other strategy you use to dispel noise much more effective. This is the main strategy employed in many workplaces with noisy environments.

Noise-isolating headphones are fairly bad at blocking out low-end sound, but active noise cancelers can kill constant tones with something called destructive interference. While it doesn’t work on incidental noise that your headphones can’t predict, active noise cancelling (ANC) uses sound to effectively cancel out loud, droning sounds extremely well.

 

But even if you’re not worried about noise-induced hearing loss, there’s another reason you should care about isolation: outside noise affects the audio quality of the sound that reaches your ear.

Isolation is the most important factor for music quality

Our biology is complex, but we don’t have microphones for ears or a computer for a brain. Instead, we have meat, bones, and nerve tissue that are very imperfect.

This is your cochlea, partially responsible for determining what sounds you hear and what gets filtered out.

While that’s not necessarily a problem, it does mean that we as humans have a few shortcomings that we can’t overcome. Namely, we’re victims of a phenomenon called auditory masking. Exactly how this works in totality is quite complex, but the long and short of it is: if there is a loud sound present (a “masker”), weaker sounds similar in frequency will be “masked” out. Ever struggle to hear someone over a vacuum cleaner or have to yell over music at a party? The same factors are at play there.

This has strange, but predictable consequences for your music. Outside noise has the tendency to mask out some notes but not others, and little noises like drum attack, string attack, and whispers will be muted altogether in the presence of louder music. Additionally, many more sounds will be quieter than you’re expecting. It’s something that is happening all the time whether or not you’re aware of it, because our brains and biology simply can’t work in a way that would avoid it. Heck, that’s even how MP3 compression even works: an algorithm deletes all the sound that would be masked by the music itself, and nearly every listener is none the wiser.

 

Wikipedia If your music’s notes are quieter than the masking threshold of outside noise, they’ll be near-inaudible.

So how to fight this? Because increasing the volume to an unsafe level in order to mask out the offending noise will lead to hearing loss, that’s not an option. If you’re going to listen to music on a commute or in a noisy area, isolation is by far and away the most important factor for music quality because of how much of your music will be destroyed by noise otherwise. All the high bitrates, accurate headphones, or enhancements in the world can’t overcome your biology (yet), so ridding ourselves of outside noise is the most effective way to improve your audio quality in those places.

But now that you know what the problem is, you can address it! No need to destroy your hearing with constant exposure to dangerous levels: we’re here to help.

Charting attenuation

It’s tough to know how well any given set of headphones blocks out noise, because even the most well-researched specs page won’t tell you the whole story. You may find that the headphones you want offer a “20dB noise reduction,” but you should ignore that number. While that number implies that a set of headphones reduces outside noise by that level, that’s not the case: headphones have a tough time blocking out different notes at the same level. More often than not, headphones won’t be able to block out certain notes at all.

To demonstrate, I rigged up a dummy head with a measurement mic jammed in it. While it’s not a $30,000USD head and torso simulator like I’ve used in the past, the results are close enough to show you what I’m talking about. By recording a test signal played over a speaker (once with headphones off the head, once with headphones on), we can get a rough approximation of what notes are blocked, and what notes aren’t.

Like so:

While I covered the more in-depth strokes in the open vs. closed back headphones article, it’s pretty clear to see with these charts just how much better closed back headphones are at blocking noise. I should mention that noise cancellation and isolation aren’t the same thing—and it’s important to know the difference.

The reason is that noise cancelling only works well on constant, easily processed sounds by pumping out what’s called destructive interference. For incidental noise like a crash, footsteps, or car horn: ANC won’t cancel it. Instead, isolation is relatively constant—incidental noise is blocked out just the same as constant sounds.

Because increasing the volume to an unsafe level will lead to noise-induced hearing loss, that's not an option.

However, isolation is hard to achieve because of so many different factors. Are the headphones properly sealed to your head? What materials are being used to block out the sound? Are the headphones themselves sealed? Even if everything is perfect, sometimes ANC will get rid of more noise because of how it works, even if it doesn’t prevent all noise from reaching your ear. For best results, combining passive isolation and active noise cancellation will dispel the most noise.

What to buy

If you’re in the market for headphones to use in noisy places, you’ll want to find a set that—at the very least—blocks out a bunch of noise. If you want to throw in ANC on top of that, even better: the more noise you get rid of, the less it will affect your listening, and the lower your volume needs to be when you rock out. This means that open-backed headphones shouldn’t even be considered for places like an airplane: you want closed-back cans.

In-ears like the Etymotic ER4SR2 are extremely good at blocking outside noise.

Great in-ears are by far and away the best isolators on the market because they seal your ear canal… when they fit correctly. Because everyone has a differently-shaped ear canal, I always recommend using memory foam tips for in-ears. Not only will they always fit, but they’ll block out a bit more noise than the silicon tips (excepting Etymotic’s Christmas-tree tips). If your in-ears don’t come with them in the box, you can grab some tips from a company called Comply that will fit your in-ears for only a few bucks. Just be sure to use their sizing chart first so you don’t get the wrong ones.

If you’re like me and have a tough time with in-ears, over-ears are your next best option. On-ears are tough because they don’t seal your entire ear: by resting on your pinna, sound can still get past the headphones fairly easily—either through the gap between the speaker and your ear, or through your ear’s cartilage into your middle/inner ear. Over ears will go completely around your ear, meaning that more noise is blocked depending on the headphones you get. But because no headphones will fit everyone the same way, I always suggest going out to brick and mortar stores so you can try them out for yourself. The better the fit, the better they’ll isolate.

For kids, you’re going to want to check out our list of headphones designed for young ears. Because hearing damage is permanent and young kiddos are super-sensitive to sound, listening to music at high volumes can have seriously negative consequences. If your children want headphones, please take the time to talk to them about safe listening habits so they don’t have to suffer from tinnitus.

Questions? Sound off below or hit us up on twitter!