How Do We Evaluate Great Noise-Cancelling Earbuds?

Author: Bond Zhao

With the recent news Apple is going to get rid of the headphone jack on the iPhone, noise-cancellation headphones are quickly gaining popularity with the public. The impression people had before was that noise-cancelling headphone units were inconvenient, with their huge control housing. This made them less than ideal for grab-and-go active use, but the new lightning cable can make control units much smaller and more streamlined than before. When the headphone is used with a lightning cable, the noise-cancellation function can be directly powered by the phone instead of having to worry about another battery or battery-compartment.

With more and more noise-cancellation headphones coming to the market, people are always getting confused on how to judge the quality and features on them. Since I am very familiar with noise-cancellation technology and acoustics, I want to give a standard evaluation you can use when looking at these headphones.

1. How many decibels can it lower/cancel out? (this is one of the most important questions people generally have about these earphones)

2. What is the Noise Cancellation Frequency Range? How wide is it?

3. With the ANC Mode on, how will it affect the acoustic and audio performance?

4. How comfortable are the headphones when people wear them?

Of the questions above, most people are only interested in the first one, but this alone is really not enough information for finding a good pair of active noise-cancellation headphones. I can say this standard is the one that matters the least, and a lot of the numbers thrown out in promotions are meaningless.

Why is that? Here is an explanation:

1. Noise-Cancellation Decibels

The number we are given in relation to decibel reduction (10dbs, 20dbs for example) comes from acoustical laboratories that run tests using pink noise. Pink noise is a relatively stable noise, and it’s a signal or process in which spectral density is inversely proportional with signal frequency.

To put it simply, pink noise is stable and consistent. However, in the real world noise is unstable, and it contains more than a signal noise, for example: engine noise, voices, construction noise, and countless other sounds. The noise we hear in day to day living is much more complex than the pink noise used in acoustic laboratories. Therefore, the noise-cancellation effect of up to 20 decibels or 25 decibels will be specific to the lab test, but not noise out in the real world. Because of this, there are other factors to consider when looking at noise-cancelling units. Basically, any noise-cancellation headphones that reduce decibels by at least 20db will be a good start.

2. Noise Cancellation Frequency Range

The Noise cancellation frequency range is the most important factor in evaluating a noise-cancellation headphone unit. As I mentioned before, in the real world, the situation is much more complex than in the laboratory ,and noise comes from many different sources in different frequency ranges. People can hear voices from the 20 Hz– 20K Hz range, so it simply doesn’t make any sense if the headphone can cancel 28 decibels, but it only works in the range of 100Hz to 400Hz. What good is cancelling out decibels in a frequency you aren’t hearing to begin with?

Therefore, the wider the noise-cancellation frequency range, the better the noise-cancellation headphone. If the manufacturer provides their spectrum, you can see how the noise-cancellation function works on different frequencies. In terms of the noise-cancellation technology today, it is optimal if the noise cancellation function works between range of 80Hz to 1K Hz, or even wider.

3. The effects of Noise-Cancellation Technology on Acoustic/Audio Performance

We are talking about a noise-cancellation audio headphones (in-ear/on-ear/over-ear), not sound-blocking earplugs right? So, in terms of an audio headphone, we don’t want the noise-cancellation function to affect the integrity or quality of the audio very much. Therefore, it is very important that the headphone designer has great control over the headphone acoustics. The noise-cancellation function will affect the acoustic performance of a headphone to some degree, but if the headphone company has a skillfully designed product, the effect will be minimal and go virtually unnoticed.

There are many different parameters to evaluate a good audio performance on headphones. To simplify things, I will list just three of them today, which are also the basic parameters we use to evaluate the acoustics performance: impedance, sensitivity and frequency range. The easiest way to evaluate this is the higher the impendence and sensitivity, the better. Also, the wider the frequency range, the better. Keep in mind though, as I said before, there are many different parameters to judge the acoustics. The three parameters I listed are only a reference, but is good to use them in most cases.

4. How Comfortable are the Headphones When You Wear them?

Comfort is also a very important factor for noise-cancelling headphones. In fact, it is a big factor with all headphones. Comfortability really depends on the industrial design and structure of the headphone. When evaluating a noise-cancelling unit, check and see if the company have considered this in their design, and if possibly try the headphones on to see if they are a good personal fit for you.

That’s it. The four considerations above can help you find a great set of active noise-cancelling headphones for yourself. There isn’t necessarily a “best” noise cancellation set of headphones, all you need is to find a product that works best for you personally.

We’re an acoustic technology company based in Silicon Valley, and currently working on an Active Noise Cancelling earbuds, which are created for daily users. Check out more:

Xin Zhao